You can give it a try, but for sure 1 GPU is way faster than several CPUs.

I still hold all my XPM from 2013, I think there is a chance that BTC-E will add XMP/USD market. If that is going to happen then the value of XPM will be close to PPC & NMC.
But first you will see a very high peak, that's where you can make the most $$$ the first few hours of trading...