You might want to check Craft Computing YouTube channel. Tom did a video with Jeff.
Both Jay’s and Jeff’s videos on YouTube are great but the topics are basic.
I think the r710 would definitively be complimentary to running Proxmox.
I follow Tom’s advice and check out Server Monkey to purchase a R420. With Proxmox running on the system it was performing well.
For me I like that Proxmox includes the web UI within a single install.
Also x2go is a great application to access the guest environments.