buying Dedicated server - what to look for

i have purchased a few dedicated servers (2) the passed couple days. 1 of them is kind of garbage for the price can run max of 5 accounts without lagging to much. this one cost me 30$ 

its using a fairly old cpu  Phenom II X6 1045T with 16 gb of ram

now for the price im not going to complain i will earn it bag no problem.

the second one i purchased was a Dual Intel Xeon 2x E5520 @ 2.27GHz 24GB DDR3 RAM

the price i paid for this one is 45$. now this one has 8 cores and 16 threads. and runs about 14 mirror clients at the same time. this is me pushing it a lil tho but still not running at 100% cpu capacity more like 90.

im looking into purchasing another dedicated server which can run 20 - 30 clients with ease. now ive been browsing and i found this one

Dual Xeon 5639 2.13GHz 12 Cores / 24 Threads 32GB DDR3 RAM. pricing for this one 55$. if my knowledge about this is correct i should be able to run 2 mirror modes for each core, aka 1 each thread. this is how i have been going about looking for my dedicated servers. but these companys have a no refund policy and i don't want to make a mistake purchasing one.

so pretty much my question. do you guys think the 55$ dedicated server can run what i want? or do you have a alternative in the same price range between 50-75$ that would do even more then what i want.

thanks