Probably not anything that will change the WEI score - it is a set of synthetic benchmarks and doesn’t rely on your Windows configuration options.
Things you could try:
Make sure your controller is operating in AHCI mode (the other option will usually be called something like “Legacy” or “ATA”). Note that changing this will “scare” Windows. If you do it on XP (which you don’t have, since you have the WEI), the system will bluescreen 7B on boot. Under 7, you’ll probably need to run “Startup repair” from your install disc. Normally I wouldn’t suggest doing this at any other time than when first installing a PC.
If your drive is attached to an Intel chipset and you’re using the MSAHCI driver, you could try installing the Intel Rapid Storage Technology driver (IASTOR). Likewise, I don’t suggest this except for new installs.
BTW, in general larger-capacity SSDs are faster, since they operate multiple sets of flash in parallel. The smaller versions of the same model just omit some of the sets of flash rather than using differently-sized flash chips, since that way they can use the same circuit board layout.
I get a WEI of 7.7 on a Crucial M300 256GB on a Dell Studio 1558 notebook.