I was recently looking for a multi-track solution with a comparable budget.
I ended up with a TASCAM US-1800: 8 microphone inputs and additional 6 line inputs. I paid 310 Euros for it, but it should be available for less than 300 USD in the States…
I use it with a standard laptop running Win7 x64 - but I had to compile Audacity with ASIO support. Runs great so far!