SSDs work differently than spinners in that when data has been written, it must be cleared before it can be written again. That causes writing times to increase after the drive has been used for a while.
Windows 7 supports the TRIM function, which does that drive clearing in the background. It requires that the drive be accessed in AHCI mode. I doubt that's available on your motherboard, with an nVidia chipset.
That said, you can still use an SSD. I've got one in a laptop PC that's a few years old, with a mobile nVidia chipset and AMD CPU. I've never run a "garbage collection" utility on it. If the write performance has degraded, it's still better than a spinner.
Note that some performance freaks run a pair of SSDs in RAID 0. The RAID drivers
don't yet support TRIM.
I'd advise against investing much money in a system with a P5N SLI SE Deluxe motherboard. However, if you wish to play, SSD prices have come down so that it's possible to acquire a 115 to 128GB drive for not much over $100US. There are some cheapish high-performance models available, if you're prepared to risk using a Sandforce 228X controller. (I have two such drives. No problems.)