yes you will see a improvement having a SSD, these type of drives are very fast, it wont matter that your system isnt on the drive.
i would recommend you go for the ocz vertex 3 sandforce 120gb SSD, this has stunning performance at 550/mbs read and 500mb/s write. also the 120gb gives you room for plenty of games.
please do avoid buying two and putting them into a raid 0 array, this isnt fully supported by windows and in my experience causes a faulty SSD within three to six months.
i do suggest you buy two, one for your system and one for your games, then you can get booted and playing quickly