Processor speed trumps just about everything else. Memory amount and bandwidth is second. Most applications such as the OS, Photoshop,etc. are much more dependent on those two pieces of hardware rather than the storage. In Photoshop, once the file (photo) is loaded, it is the memory and processor that determines the speed. When you apply filters, crop or edit in any way it takes place in the memory and cpu. Much of the OS loads up into memory and stays there. Boot time is improved a bit my SSd's and other functions requiring storage access. Lastly since it is easy to upgrade a disc and not a cpu, I say buy the best cpu and memory configuration you can as top priority. Remember in the SSD laptop only the OS is on the faster storage. The rest of your programs and data will be on a slower HDD (5400 vrs. 7200).
No SSD will not improve the performance of your CPU. The only time you'll notice speed improvements are booting and program launch. Soon you won't even notice that. Buy an SSD for reliability and durability and in a laptop for power conservation, not speed.
An SSD will definitely make your processor FEEL a lot faster.
An SSD will make the computer seem much faster, overall. CPU-intensive tasks are among the few situations it will have no impact on.
A faster CPU is adviseable only if you use demanding applications, suchs games or AutoCAD and the like. If you are an average user, an SSD will have a lot more impact on your computer's performance than a CPU a few hundred megahertz faster.
To be honest, those 400Mhz will be barely noticeable, while an SSD will make the machine a lot more responsive.
Some laptops have a mSATA slot in them, in which a SSD may be installed, independently of any other hard drive. If you get a laptop that has this slot (even if nothing is in it when you buy) you can always add a SSD yourself later.