Yeah, definitely go for SSDs, if you can settle for the space.
This motherboard have a build-in raid controller, at almost the same price of the standalone raid controller:
http://www.servethehome.com/Server-detail/supermicro-x10sl7-f-motherboard-review-haswell-intel-xeon-e3-1200-v3/
I would go for a SuperMicro motherboard, and a 1200 v3 series cpu. You'll get better support in ESXi (atleast some realtek nics are unsupported), IPMI and ECC ram. The price is pretty much the same last time i looked.
If you want to save money, there are amazing deals on ebay for used servers...
What about Proxmox? We only have 3 esxi servers at my work, so we are pretty small. But in my lab I've set up Proxmox, and I'm very surprised at how good it is. I am not missing any features from esxi, better driver support, and way easier backup.
What are your thoughts on Proxmox in a...