Not even close to enough information to be able to offer any type of operational reccomendations.
What is the current bottleneck? What are the failure conditions are you seeing? What part of this software is resource-intensive? Etc.
Be *extremely* wary of any company that says "yeah! we can do that!" without asking these questions, as well as having a qualified technician load-profile your current machine with problems.
While it could absolutely simply be incomptence by your current host, I would say more likely it is either a programmer who entirely does not understand how to write scaleable code with performance in mind (e.g. really blatant stupid implementations of things), or that whatever you have simply cannot be done on your current level of hardware.
So.. basically without entering a real dialogue with a reputeable managed hosting company, you will won't be able to get a real answer
Hit me up if you're interested in Reflected, I would be happy to take a look and see what/if there are any recommendations I can make in regards to configuration/hardware setup.
(phil at reflected.net)
Hope this helps some!