I think it's time to replace, personally. You'll find the newer CPUs from both major manufacturers to be very fast, and the PCI-E options will open up of course. I went from a single core 939 to a quad core intel and HOLY SHITBALLS it's fast! Then I overclocked the piss out of it and said HOLY SHITBALLS once again. I have yet to tax the CPU, even if I run dual SMP instances of folding@home and play call of duty at the same time, along with trillian, MBM5 etc.
The other thing to think about is the MSI board will kill its capacitors sooner or later, if it hasn't already begun to show. My neo2 platinum, strangely, is still running fine as a media box, but my neo4-F killed its caps and I replaced them. So it's still running fine, but not without slightly delicate surgery. ALL my previous MSI boards before 939 died and I tossed them, so mull that around in your head a bit as well.
Oh and don't forget to add PSU to the list of items you need to upgrade
