I did a whole thread on this over here.
http://www.karaoke-forum.com/viewtopic.php?t=18436
Just about all VST's require the same thing, CPU. It's really hard to get close to realtime with any of them. The newer i7 Intel CPU's will come close.
That being said, if you want to run near realtime VST's you'll need to look into the realm of DSP addon cards.
I use an Emu1820.
http://www.emu.com/products/product.asp?product=9871
Universal Audio makes the UAD
http://www.uaudio.com/products/uad/uad2sl/index.html
I use reaper for my DAW
http://reaper.fm
The setup pretty much rocks. Combined with a midi controller it's like having a digital mixer that I built, and can reconfigure at a whim.