The best impressions on tips I've found were posted by
@Jobbing on the Adel thread. By far the most extensive and detailed impressions I've seen. I got the Spinfits and really like them over any of the tips I got with my ADELs. As mentioned above, I would order from Earwerks, now Empire Ears and get the set that comes with several of them, so that you can try what's best for you. To me, the Spinfits are the most comfortable, they give you a better seal and I believe the sound is the best coming out of these. Not sure how to post the link to the tip impressions, but I've copied them below, but credit goes to
@Jobbing for these impressions:
1964 U6ADEL – tip comparison (edit 1 09/29/2015)
Disclaimer
I don’t consider myself to be an audiophile with golden ears nor am I able to provide you with a scientific approach, but I’m sure there are lots of (self-acclaimed) experts willing to do so with excellent measuring gear. I’m just giving you my honest opinion here 
. In general I consider all tips in this comparison to be of very good quality and frankly you can’t go wrong with either of them: to me it’s a matter of marginal differences and preferences when using these on the U6. This overview might be subject to changes
Tip size: M, except for the Sony Hybrids
Prices: may very
Test tracks (24B):
- All this love – Angus & Julia Stone
- The Fear – Ben Howard
- Wonder – Natalie Merchant
- Giving up Everything – Natalie Merchant
Important note: U6 has a 3D printed housing, its sound tube to me has rather sharp edges, as a consequence insertion in the ear canal may be a bit uncomfortable especially when using thin silicon tips (shorter than Comply) so make sure to pull back your outer ear when inserting soft silicon tips in the canal. The nozzle doesn’t have a ring (see EarWerkz Supra universal in comparison) to prevent tips from sliding off when pulling it out of the ear so please be careful using small size tips as they might get stuck.
1964 U6ADEL (L) and EarWerkz Supra (R) for reference regarding nozzle and flush fit
Tips - Line up:
Comply - SureSeal M - SureSeal M+ - Saroundbi SpinFit - Muse SpinFit - Sony Hybrids - OS200
Comply™Foam (T series ~$7 a pair)
+ best isolation (especially high tones)
+ easy seal
- (de)compression
- hassle
- short lifespan
- no wax guard
- price
Comply has always been my last resort for tips and for isolation purposes only so I’ll make this story short. Compared to most silicon tips the Complys tips are about 2 mm longer than the average silicon tips and the front foam part will act as a buffer and well prevent the nozzle’s edges from hurting your ear canal. The foams provided don’t come with the earwax guard filter like the TX series.
Aurisonics® SureSeal™ (SK4-SST_S3 ~$6 a pair)
+ Slightly ‘airier’ than Comply
+ very comfortable for long listening sessions
+ instant seal due to ‘stickiness’ of the silicon
- jelly-like silicon makes isn’t very practical when sliding the tip over the nozzle
The SureSeal (regular M version) are made of a thin ‘jelly-like’ silicon. Although just a tad less bass quantity the SureSeals sound more spacious and ‘airier’. To my own surprise they make a very good alternative tip for the Comply. The highs however are more present now and seeming to be fatiguing for longer listening. If pushed too far over the edges of the nozzle will be visible. Beware that the stickiness of the tip and the lack of a ring on the nozzle
may cause the tip to be jammed in your ear canal very easily.
SureSeal M+ (L) and SureSeal 'regular' M (R)
note: the alternative M
+ tip (yes, the one with the ‘nipple’
) does elevate the mids and highs making the sound slightly ‘airier’ compared to the Comply but thinner and bass south from neutral, a bass-drainer so to speak.
Saroundbi SpinFit® Donguri (SPFT RD-01M ~$10 a pair including postage)
+ flexible
+ all round tip
- isolation
In general I prefer the smallest size SpinFits (XS) on my IEMs for deep/maximum insertion. Due to the U6 semi-hard shell preformed limitation I use size M for best seal. To me Saroundbi SpinFit Donguri (Japanese) bests the Comply and SureSeal in overall clarity. Mids and bass are more prominent compared to the SureSeals.
Muse™ SpinFit (CP101 / CP100 ~$5 a pair including postage)
Besides the slightly (perceived?) increase in bass quantity I can hardly tell the difference between the sound coming from the Muse (Chinese) and Donguri.
Saroundbi SpinFit (L) and Muse SpinFit (R)
Optically the latter
seems to be a fraction thinner, not noticeable in my ear though. The Muse version however is half the price making it a bang for the buck if size fits your ear: afaik Muse SpinFit is only available in size S and M
Sony Hybrids (EP-EX11LLB ~$10 a pair including postage)
+ very flexible tip
- isolation
- too much bass presentation to my liking
Due to the high flexibility I prefer the extra large size for the Sony Hybrids. These are an extreme good pairing if you’re looking for that extra bass while retaining the quality mids and highs.
JVC Spiral Dots
Suggested by @vtkc to include in this comparison, unfortunately I don’t have them at hand. Will add my impression asap.
Ostry OS series (OS100, OS200, OS300 ~$10 a pair including postage)
The Ostry tips resemble the SpinFit silicon tips soundwise and optically.
Saroundbi SpinFit (L) and OS200 (R)
In addition they have a metal mesh/filter supporting the soundtube and pre-shaping the nozzle to preventing its edges from hitting your ear canal. To my ears the metal mesh/filter doesn’t affect the sound therefore preventing the nozzle from clogging up as a bonus.
The OS series come in three versions each offering different levels of ‘sibilance control’.
- OS100 - lowest impact on sound : smallest reduction of sibilance (blue)
- OS200 - medium impact (red)
- OS300 - highest impact on sound : largest reduction of sibilance (black)
I found that the OS200 resembles matches the Saroundbi SpinFit Donguri and OS300 is between Muse SpinFit and Sony Hybrids. My personal preference is the OS200.
Final words
It’s very understandable 64 Audio included the Comply tips with their 1964ADEL Kickstarter models. They act like buffers between the rather sharp edges of the 3D printed housing/nozzle and have premium looks. In my comparison the Comply has the best isolation. If you’re not looking for optimal isolation on your universal monitors, the alternatives are very good and affordable compared to the Comply tips however should be used with care. Overall winner and go to tips for me would be the Ostry OS series.
edit 1: added pictures of U6 and Supra, side by side as a reference point
Jobbing 
