Probably, the best alternative, and I have done this with an M2A-VM board that I have, is to get a faster dual core and also add memory. I did 2.5 to 3.0 GHz upgrade with 4 GB mor ememory, and the system performs noticably better in every resepct.
If you do not have the software or operating system to take advantage of a quad core processor, it will not do you much good.
Asus/AMD motherboards can be overclocked. Alternatively, overclock the processor you have, within limits, and with better cooling for the processor you have or a replacement processor. I would think that more memory helps only if you are running a system that can use it, or if you are so low in RAM that you are using virtual RAM on you hard drive. What is your operating system? A 64-bit, versus 32-bit, will run faster, for example.
As far as the life of a motherboard, who can tell? I have boards that are several years old and alive and kicking. I had to have a brand new full-sized ATX board replaced twice (under warrantee, luckily) within a few minutes of installation. Fortunately, all the rest of that computer was perfect and ran with another motherboard without issues.