...with rack versus floor based effects, I would consider what type of interface would work well for you. Do you like to simply turn a nob until it sounds good (tactile control), or are you comfortable scrolling on a LCD and adjusting 4 seperate values on a chorus patch?
Some folks love to tweak things, others want to get a usable sound quickly and be done.
I have an older digitech 2101 artist that I love. It is highly programmable and with the dual processors, it can create just about anything you want, even lush synth style soundscapes. But, it was a pain in the a#$ for me to learn how to use well. I got it early on in my switch to electric on advise of a friend, and without a good idea of what I wanted to get out of it, it was a pain.
so thats my advice, pick up something that is compatable with the amount of time and energy you want to put in to it... S.