"I don't want to get too crazy after the purchase of the headphones" ... I've said that before, lol! You're going to own like, 10 amps some day, my friend! I've learned it's better to pay once and be done with it. You'll save a lot of money that way. Just my two cents.
But since you ask... the O2 sounds pretty darn good with the T1. It's punchy and clean and it can get plenty loud. However, I think there are better options available to you, if you're smart with your money. The For Sale/Trade forum actually has some really good options right now:
This guy is seller with +20 positive feedback. He has an Asgard 2 with shipping and Paypal included for $195:
http://www.head-fi.org/t/774489/schiit-asgard-2
Here are a couple of options that cost a little more, may help delay your upgradeitis for a bit:
Here's a dude with +36 positive feedback selling a barely used Valhalla 2 for $300:
http://www.head-fi.org/t/754017/mint-schiit-valhalla-2
And here's a Bottlehead Crack with shipping and Paypal included for $340:
http://www.head-fi.org/t/772308/bottlehead-crack
... Those amps will be a little more now, but they'll probably end up saving you money in the long run. Also, I don't know any of these sellers, I'm just telling you the deals I'd be looking at if I were in your shoes, based on my experience. I will say... generally speaking, I've found Head-Fi traders are about a million times easier to deal with than Ebay sellers!
Good luck!