One thing you should know about ESX, if ALL VM's are the same OS architecture, VM Ware can actually share the CORE, and memory requirements are 30% less right off the top. So that should reduce your RAM from 3 to 2.
The next thing is, since the drivers from the VM Tools are generic, you don't have to worry about vendor based driver support, plug and play, and they don't have to work as hard to manage the hardware. The overhead for each VM is less, and I would say (in my experience) is another Gig.
So you are now at 3Gig TOTAL for all your VM's (1 gig each). I would speculate that you really don't need that much RAM. I fight with developers all day long about memory. I will bet any amount of money, there isn't a single Windows Machine with conventional software that \*NEEDS* more than 2 gig of RAM.
I have yet to see it, or have proof of such an animal. I see wasted memory, uncessary running programs, running multiple programs side by side that shouldn't, programs that take the RAM, reserve it, but ACTUAL usage, just isn't there. So I would reduce each one of these VM's to a moderate level, like 1Gig, and check the performance tab in Task Manager, you might be surprise you have way more memory than you will actually use.
SQL, does have high memory requirements, but you can reduce the other 2 VM's with no problem, maybe leave SQL at 2G, but try it at one to see what happens.
