Your thinking is correct.
HOWEVER, check the size of the OS you currently have vs. the size of the drive. 40GB may choke Windows 7.
Read other posts about SSD. You want to have 15-20% free space on a SSD, for it to optimize itself. On a 40GB drive, that's 8GB that should be left unpartioned and unallocated. THus, only 32GB of usable space.
I have 2-Intel X25-V 40GB in RAID 0, for my OS and Programs. I (used to) approach 46GB of used space. BUT, I wouldn't dive into RAID if you don't know about it. PLUS, I've lost some of the special features (TRIM) having these 2 in RAID (a whole other post).
Once the OS is installed, reads will be most important. Still fast!