Multiple track recording with VST's - Lag (XP + 7)

Hey, I recently fixed my desktop Pc to move from my Dual core 2.5ghz i5 laptop back to my quad-core 3.5ghz desktop PC, this is less of a problem more of a disappointment however.. more than 7 tracks recording at once from the same channel on my Mackie blackjack with a few VST's (X50 amp + TSE 808) and I am getting clicks etc etc. My laptop has been able to handle quite allot of vst's on at least 4 channels + 1 midi for drums whilst recording. I was using Windows 7 64bit on the desktop PC but I had to wipe it and dual boot since Reaper was doing the clicks with only 4 lanes record enabled!!! Is this about right? How would I use an 8 input Onyx blackbird when I update my Blackjack if when I am using guitars direct in there is going to be this problem? My latency is low at 14ms set up to normal + 512 samples. If anyone has any information about this it will be very appreciated. Thanks!

update 

Mild crackling at 7 severe at 8 channels (duplicates), 64 bit and 32 bit tried bridging the plugins from 32 to 64 and vice versa. The cpu is only at 24% my Mackie blackjack is set up with the latest (3.0) drivers on Low latency mode at 512 samples getting 13ms latency. is this normal?! Also: - The same happens at 8000 samples on extra safe settings, except it's milder clicking with 8 tracks. I've tried xp 64bit aswell as 7 64 and I don't think it's worth trying 7 32 bit? It was a massive pain to get xp 64 working without a disk drive :3 This is driving me nuts, any contribution / idea would be a great help. - my HDD passes S.M.A.R.T testing it's a SATA barracuda 6gb/s 7200rpm 16mb cache

I CAN HAVE 25 TRACKS WITH THE SAME PLUGINS x86 IN CUBASE 5.1!!! -- no clicks or lag This must be a problem with Reaper???