I'm just looking for a very portable amp that can sufficiently power these. The lower the price, the better. I want to use them around the house an to places outside the house like school or the library so a small portable amp would be nice
These headphones are both open. I don't think it would be suitable for usage in a library or school as you will have sound leakage. You might want to consider a closed can.
To answer your question though, I only own the Q701 and haven't heard the DT990. I think any portable amp will do as I don't think these things really require a ton of juice to get loud. I don't have any experience with portable amps though so keep that in mind. You might even be satisfied directly out of a phone/portable device. I've listened to them out of my Galaxy S3 and they sound good. They do scale nicely though with better equipment in your chain so they will give you plenty of room for upgrade.
I'm not sure what would be considered "properly" amped for a Q701. I've listen to them out of my S3, a Vali, a Magni, and my Lyr and I think they scale well with more power as I enjoy them the most when powered by the Lyr but still enjoy them even out of my S3.
Let me know if you'd like me to go into any more detail about the Q701.
Thanks! Honestly i didnt even know these were open! (i feel kinda dumb ) but in terms of the q701s, do you think an ipod would have enough juice to power them to a reasonable degree? Also, im new to this headphone thing so im not completely sure about amps and the such but is there a good portable headphone amp under say 50-60 dollars that will efficiently power the AKG q701s? this will all run on my ipod and my laptop computer. but yeah i think ill still like them even if they are open.
If I were in your shoes, I would try the headphone straight out of the iPhone first and see what you think. I think the iPhone can drive them to a reasonable volume. After spending some time with them and you feel like you'd like to upgrade your chain then you'll have a better grasp on what you'd like out of the headphone and can pair an amp or dac accordingly. Contrary to what most people will tell you on this site, I don't think the Q701 is that hard to power. But again, I do think they scale really well with nicer gear.