The thing is, the SSD advantage would be nerfed by the cable / interface bandwidth limitations.
Have you checked whether your model has room for a 2nd drive ?
Not long ago we tested two laptops configured identically as follows:
a) 120 GB SSD + 7200 rpm HD
b) 7200 rpm SSHD
The test ran 6 weeks w/ 5 users and they were unaware that they were not identical. Both had a 120 GB boot partition so the looked the same in Explorer.
Tho I'm sure that benchmarks would have shown a significant differences, no one ever noticed any difference in performance. And the reason should be obvious ... folks don't generally do disk intensive tasks in their normal usage.
To address this in the future, you might want to have your lappie custom built...