Ouch, still 2 and half years isn't bad for a set of headphones. What's up with the mi's anyway? Know what you mean about the monster turbines. The bass on those gave me a headache as well. I think it's to do with the fact that the bass swamps the details so you turn it up to hear vocals etc more clearly and end up with a headache!
Just a thought but if you can a)wait and b) stretch to cover impressions and postage (don't know how much they are where you are for impressions) and want to stick with customs you could do worse than have a look at Cosmic Ears single ba which is going for a £100 atm. The downside is they aren't taking orders until the 20th after clearing a mammoth backlog though so you wouldn't get anything back till January at the earliest. They are also acrylic not silicone if that makes a difference.
Good luck getting em sorted.
The left monitor in my Mi's developed a bit of a crunch/crackle noise on certain tracks (tried difference sources, different versions of the track ie. YouTube Vs. my own FLAC rip Vs. my own CD) and I returned them to Minerva. They said there was a bit of wax blockage in there and moisture ingress which dropped volumes by 4dB in that monitor, which was said to be 'barely noticeable' . £12 to remove the blockage, £137 for a part rebuild or £205 for impressions and full rebuild with 12mo warranty... I picked the cleaning option, got them back and the left monitor is now quite even worse than when I sent it in. Much lower volume across the board, almost silent in some parts of some tracks, the audio quality is much reduced and the crunch/crackle is still there. My left ear is, as proved by hearing tests, my stronger and more sensitive ear so it's like my whole world has been shattered even if I've been tweaking EQ's and stereo balance settings to try to alleviate my issue and smooth things out.
The part-rebuild option doesn't take my fancy and it could easily be 6-12 months before I am readily able to afford a full new build with impressions (£205 is what I was offered and includes postage + new impressions, as opposed to the £215 normal). Plus, Lee Kennedy back in the day set me up with a certain kind of filters inside the Mi-1's as I found the standard sound to be a bit ... opposite of intimate ... and a bit, well I can't remember but I did review them and Lee fixed me up with a custom filter set which was epic for my tastes. There's no guarantee I'd be able to get those back either.
As far as customs go I've only ever had the Mi's and those were fantastic. I'm not sure I'd like to risk £100 and more I'm assuming for impressions and other bits on new, single driver custom made from acrylic. They could be fine but it's a fair chunk of change and I know universals are reasonably comfortable for my ears with single/double/tripled flange silicone or Comply foam tips.
Until I get financially back on my feet, £100'ish is the max I can spend and I think it's likely to be best spent on some universals. I can't live with my Dad's Meelcs for another week :D