Ah thanks, I think solid state sounds okay for me. I was looking up some more portables around $50-75, found e7 and this
Headroom are on sale. The e7 can be used while charging so that would be a big plus, and it seems to have more battery life as well. Can I still use these with my USB x-fi (via the amp's aux-in), I think read somewhere that its not advisable to bypass the DAC?. Headroom uses AA batteries which is kind of lame, but reviews / opinions say its of higher quality. Which do you guys think is a better buy for gaming + bassy music ? (I will be using the DT990 pro/250 ohms by the way)
Have you read Head-fi'er ClieOS amp round up? It includes impressions of both for amp quality. Last I read, the Headroom AirHead and BitHead (same amp, BitHead adds a DAC) are decent but of aging design, and even FiiO's inexpensive amps sound superior for less money. But opinions aside, consider some spec facts: the E7 is an amp/DAC combo. You already have a similar-quality DAC in your USB X-Fi, so that part you're paying for in the E7 is redundant/extra-but-useless. The amp section of the E7 isn't a big upgrade in power either, about the same as an iPod, FiiO E5, and possibly your X-Fi. In fact, I believe the E7 amp is basically the E5's buffer connected to a DAC section. I think I read that FiiO is releasing an updated E7 with the E6's amp buffer... about the same amount of power still, but a bit cleaner performance.
In my opinion, based on my research, you would be better served with a FiiO E11. Much more powerful amp than the E7, no DAC that would be useless if you are using an X-Fi's DAC anyway, rechargeable lithium battery, and only like $60 if you buy on Amazon from seller Micca with a spare battery (so you can keep a spare charged & ready). A good deal. If you can afford $100, your DT990 - 250Ohm headphones would be even better served by the more powerful E9 desktop amp.
Pox64,
I fully understand how wires can be an issue. Especially in areas of traffic or where you want to be a little discreet. Just decide for yourself if the trade-off of permanently allocating part of your purchase budget towards a wireless antenna, cheap built-in DAC, cheap built-in amp, cheap built-in battery, and the weight of those components is worth the wireless convenience. I'm going to assume based on your Bluetooth mod on your Senn HD 25-II that you have the modding skills to replace the headset's batteries when they no longer hold a charge. I personally have no idea how the wireless Sony headset you mentioned sounds, Sony makes pretty good products, but I wouldn't believe it sounds better than my Q701 wired into a decent amp/receiver. The Q701 also comes with two long lengths of detachable cable, so I have no problem lounging on a couch while the cable is routed mostly out of the way. IMO, the inexpensive flagship AKG headphone would be the clear all-around choice among those listed
for my tastes, especially considering you already own a pair of wireless headphones. I can't tell you if they'll fit your preference for sound signature, but technically they are very capable and high-performing headphones.
. I don't really care much about having to charge the amp daily. Also I found one of these http://us.store.creative.com/Sound-Blaster-XFi-Surround-5.1/M/B0017QQQAE.htm lying in my basement, I believe these have CMSS 3d, will a USB card work better with the tube or e11 ? 
