Hiya....there are some very general statements there, and we probably need to delve a bit more deeply. Can you first post the exact spec of the solaris machine you have ?
What version of Solaris? Is it Sparc/intel ? 32/64 bit ? how much memory, how many physical CPU's, what model and speed CPU's, how much disk and of what speed, and whether there is hardware or software raid ?

Then I think you need to qualify the statement that the performance is "perfectly normal". SAP may be running normally on 1 CPU, or it might be using all of them. We need to get some proper measurements of the performance of the machine over an extended timespan. This article shows you how to measure such things, especially tools like "sar" that can collect data, historically over time.

Once you have that data you can then start making decisions about what new hardware you can run it on.

I hope this helps...