Hardware Questions for Hyper-V with 2-3 VM's

Hello All,
I'm currently setting up my server for my new office and it's the first time I've decided to jump into Hyper-V or any virtualization for that matter. This is what I'm setting up:

Host = Windows Server 2008 (Not R2) with Hyper-V role only enabled.
GuestVM1 = SBS 2008 for our database apps and Exchange. Currently there will only be about 10-15 mailboxes on exchange.
GuestVM2 = Windows Server 2008 with Terminal Services role only. I will have 4-5 people connecting to this server at all times.

My question is, what would a good setup be hardware wise to not have any performance issues. The server I currently have I suspect that it's not enough juice for it all.

I don't have a huge budget for everything, so I'm trying to figure out something between minimum and insane.

Thanks in advance for all the help and tips!

EDIT:
My current server is:
Xeon X3220,
Supermicro PDSMA M/B
8GB DDR 2 Mem