Well, it will be important for you to do a considerable amount of research for your individual needs. What is "versatile" to you may not be very useful for me. You will need to plan out exactly how large of a case and power supply you will need in the long run (not just right now). Are you interested in manipulating samples in your rack, or do you just need a good monosynth built to your specs? How many simultaneous voices do you need? Are you just wanting to sample the sounds of your rack into Logic, or do you hope to perform fleshed out compositions?
What exact problem do you see eurorack solving for you that you can't achieve now?