Are you open to running Windows 8? Do you have a TPM chip in your laptop, and is your laptop UEFI capable?
There are TCG OPAL SSD drives out there. I have not found a Sandforce based drive that supports this, but Micron has one: Micron C400 SED. You have to make sure you buy the SED version, not the plain version. Using an OPAL compliant drive will allow you to use Bitlocker in Windows 8 in conjunction with the drive's encryption (which it's already doing).
Bitlocker in this scheme does not actually do any encryption from the system side (at least for data read/written). The bulk of Bitlocker in this mode is acting as a "Gatekeeper" since SED drives still need a means of access control to unlock the drive. When those are activated in this mode (with W8 and Bitlocker), the drive is initially locked and the system will only show a very small "shadow partition" under 200MB. This is where the W8 boot files are stored and the unlocking in Bitlocker happens with it interacting with TPM to pass a key to unlock the drive.
If you don't want to go Windows 8, you lack TPM (though I assume you have it since they asked you to enable bitlocker), or BIOS instead of UEFI there are a number of software products that can manage SED drives in place of Bitlocker.
In my experience, Bitlocker does in fact have a noticeable degradation in performance even with HDDs. With SSDs, the comparisons I've seen seem to indicate the degradation is worse, perhaps enough that a lot of the benefits to SSD is reduced. In my view, a SED based SSD with Bitlocker management (or another software piece) is the best way to go.