I've not used the products you mention (well, I've played briefly with TrueCrypt and it is on my ever lengthening list of "things to investigate further"), but I doubt a well designed encryption solution would impose a significant hit with a modern CPU to churn calculations through.
There will be a CPU hit that will reduce bulk read/write performance, but it is unlikely that this will be nearly enough to mask the difference between a good SSD drive and something slower.
It certainly won't touch the random-read performance gain you get from moving from spinning disks to good SSDs - the near-zero latency compared to several milliseconds potential head-movement-and-waiting-for-the-right-sector-to-spin-past delay is going to be much more significant.
The random write performance hit that might be created if the encryption solution needs to write whole blocks (that are bigger than a standard drive and filesystem allocation units) is going to be dwarfed by the fact the SSD probably has to write whole blocks that are larger. You might have to be careful to try make sure your filesystem blocks and the physical drive's block arrangement neatly align with each other because uneven overlap could cause significant speed drain for many I/O patterns, as seen with newer spinning drives based on 4Kbyte sectors when the OS assumes any multiple of 512bytes is a safe alignment strategy for it's 4Kbtye blocks).