Would it be cheaper to piece together a supercharger?

I see head units go for good prices on ebay. I'm only looking for an a-trim right now (since I have stock replacement rings ) Would it be cheaper to buy pullies, and other small parts and head unit seperately? I found a company that makes a nice billet bracket for the vortechs.

I have my eye set on an a-trim because they seem popular, and upgradeable should I change my rings How are Paxtons? do they all mount on the drives side or is that just the intercooled ones?

Oh yeah, are paxtons/vortechs rebuildable? Is one much cheaper to do than the other?

I think I am going to, Most people sell the head unit, brackets, pullies and belt. I'm looking for an FMU right now...I like the Powerdyne FMU because it goes right on the factory lines....