Need to build a small office server

Greetings all. Looking to build a small office server with a budget of around $3,500-$4,000.

Will be running Windows Server 2012. Programs will be Quickbooks Enterprise and a reservations program. Max users connecting will be 10.

I have built PCs for 20 years, and the last server I got was about 5 years ago and I bought it from Dell. I'm hoping doing a self-build will be cheaper, but not sure what's the latest and greatest in server hardware.

Will dual processors be beneficial?
Can I get by with AMD processors?
Anybody using ssd's for servers?
How much memory?
Anything else I need to consider?

Thanks for any help you guys can offer.