That's not enough to adequately power the 600 ohm version. Don't get the 600 ohm version unless you're using a high output impedance amp like an OTL tube amp because you can get the 32 and 250 ohm versions a lot cheaper and you will have a lot more usable volume. The 600 ohm is not "better" overall, that is a myth. The 32 and 250 ohm versions are equally as good (based on what amp you're using, as I mentioned).
If it were me I would get the 32 or 250 ohm 880s, basically whatever I can find the best price on which is usually the 250 ohm Pro, and an O2. The magni is supposedly a bright amp and that usually doesn't match well with the 880s. The O2 is more neutral.
Down the road you can add a DAC, something like the Stoner Acoustics UD110 or HifiMeDiy Sabre DAC, which are both just $50. For now, if you've got a relatively new mid- or hi-end motherboard then your sound card will probably work pretty decently as a DAC. Make sure volume is maxed out in Windows and in the music program you're using. I'd also try ASIO and/or WASAPI to see if they provide an improvement. ASIO provides a slight but noticeable improvement on my MS2 and MS2+. I haven't tried using it with my motherboard's built-in sound card but I suspect you could gain a little sound quality there as well because the Windows sound mixer can degrade the signal and ASIO and WASAPI completely bypass it.
I just got my little brother that same setup for Xmas-- 32 ohm DT880 Premium and an O2 w/ rear power . Add one of the aforementioned DACs and you're probably coming pretty damn close to the sound quality of my setup (G109 & MS2+) which cost just under $800. A very good setup indeed, especially for the price, and potentially an end game setup if you can avoid the itch to buy other headphones and amps.
Oh, this is all assuming you're talking about a desktop setup. If you'll be using them for portable listening I recommend no higher than the 32 ohm version and you'll still need a portable amp to get the best out of them.
ASIO: http://www.asio4all.com
EDIT: Chris J and I will have to agree to disagree. I've used several amps and sources that supposedly had enough to power my 600 ohm 770s yet I couldn't get quietly recorded tracks to play anywhere near loud enough for my tastes.