K701 to ...........

I like the 880s better. They are similiar to 701s. Less soundstage but close as well as detail but have more bass. You really need an amp period though.

Switch over to a recabled Denon D2000 or go with the D5000. My can before the D2000 was the K701 which I loved, but wanted something closed with a bit more bass. I couldn't be happier with the upgrade. The recabled D2000 gives me all the details of the K701 but with the thumping bass that the Denons do so well.

Whoa...get an amp for those K701s STAT! I just realized you weren't using an amp with the K701...you really need a decent one to bring out the best in those headphones. I ran mine with a Meier Headfive and they sounded excellent. A good quality warm amp will do the 701s well.

I went from the 701 to a pair of SA5000s, they are over @ moon audio right now getting the blackdragon treatment, getting those babys balanced!

I have DT880s and K701s. I find them quite similar, but I normally reach for K701s because I find them slightly more refined and with better sound stage.

The 990's have an impressive 'thumpy' bass, but the mids are very recessed, and the highs are simply too bright. The 650's are better in my opinion. They have excellent bass.
The 650's do not quite have as much bass as the 990's, but the bass, mids, and highs are much better balanced than on the 990's.

none of these cans will be any good to you without a decent amp

ibasso T1 iirc is a portable amp and may not have the juice to drive your K701s or any of the suggested phones to their potential

strongly suggest amping, for me the Heed Canamp did it, but then again I never found the bass that lacking. relative to phones like the DT990/HD650 of course, but in its own right the bass is perfect.

it just needs the juice!

I agree that buying a different can will not really solve the problem as you need a high quality amp first to be fair to the k701s.

One more vote here for an amp for the K701.
(I can recommend on the SOHA and the doge 6210 as amps that have great bass control with those cans)

Also, I don't know how much playing hours your pair have, but IMHO for getting a good bass you need at least 350~400 hours on them.

Ditto. Don't reliquish the K701 until you've given them a try with decent amplification. Mine pair very well with the all-tube DarkVoice 336i and the hybrid Bada PH-12.

Tubes definitely do justice to the K701, bringing out tonal and textural richness, as well as nice dynamics. No thinness or sterility here, folks! Just a whole lot of "just-rightness" in all respects (IMHO)! : )

As others have said, you need an amp for the K701 in order for it perform anywhere near its abilities. I personally used mine with an M^3 with bass boost, and the sound was fantastic.

The HD650 and K701 are very complementary phones. I'm in the process of selling the AKG, but only because I'm downsizing and prefer the Senns for their superior comfort.

I've also owned the DT990 and DT880, and I prefer the DT880 a lot more. The DT990 was a little too thumpy for me, and I found the highs sibilant at times. However, I think the K701 trumps both Beyers.

If you like the K701 signature but would like more bass, I would highly recommend picking up an amp that has a bass boost feature. This really made the K701 sing for me. Tube amps are frequently recommended as well, but I have no experience with those.

unless you're uninformed, why even buy a k701 unless you had a suitable amp to drive them with?

I drove my K701's with a HeadAmp GS-1, and still could not warm to their sound for some reason.