I think, for vps purposes, memory is more important than CPU.
For your budget you might find a quad core, I would suggest taking at least 4 GB of ram with it.
» www.InstantDedicated.com - Online in no time » Dedicated Servers in [EU] Netherlands with DAILY support, also on weekends » DDOS Protected network - 100% Money Back if it doesn't work for you » Streaming / IPTV allowed | Up to 10 Gbit ports | 100% Network Uptime
I want to host 3 vps in 1 dedicated server with independent control panels
When you're talking about independent control panels, are you referring to eg. 3 cPanel licenses since they are all on different VPS. If that's the case, then you'll totally need to increase your budget quite a bit more.
cPanel on 1 VPS would cost about $15. So 3 would be around $45 per month. Taking that off the $120/month budget, it's going to leave you with around $75/month for the server. That's not going to be enough to get a decent looking server.
By the way, since you're splitting it to 3 VPS, you'd need at least, bare minimum a Quad Core. As for RAM, it depends on how each site over there is going to eat up your RAM. But since you're on 768MB RAM and still OK, I guess having about 3-4GB RAM should be good enough for you.
With that, I'm still talking about bare minimum. Not even going further from it yet.
Dedicated Servers - 100TB Servers - 100Mbps Unmetered Servers - Web Hosting - CDN Network
Servers in Central, East/West Coast USA, EUROPE and ASIA
Welltodo Century - www.welltodocentury.com