With Pianoteq, I had fine results using an old USB sound card that cost about $50 in 2006
along with a basic USB MIDI interface to connect the keyboard to my laptop
If money is an issue, and you do not find the need to connect the MIDI directly to the soundcard, I think you'll do fine with a similar approach -- and you won't need to shell out for the high-end gear. A USB soundcard around $50-100 (something like this
) and a USB/MIDI interface (something like this
) should work. I haven't researched that particular model of sound card, though, so it's a good idea to see what the best-reviewed USB card in that class would be.
The only reason I had a USB sound card, incidentally, is because the on-board sound on my laptop is busted. If you haven't yet, I would see if your internal sound can handle Pianoteq without resorting to an external card. You can test that without hooking up your actual keyboard (by clicking wildly along Pianoteq's virtual piano).