What exactly are you trying to get out of your sequencer. I'm a little confused if you're looking for basic sequencing or something advanced to use along side something basic.
I'd spend a couple of days looking through manuals and watching Youtube videos around the following sequencers:
1. Eloquencer
2. 1010 Music Toolbox
3. Micro Ornaments and Crime in "Sequins" mode.
4. NerdSeq
5. Tiptop Z8000
6. Pittsburgh Modular Electronic Sequence Designer
Each of them have their strengths and weaknesses of course. You're looking around $500-700US for each except O_C ($250-300) The Pittsburgh unit is also available in a stand-alone case for $50 more; which extends the life of your rack in terms of available HP. There are plenty more solutions out there. But at the end of the day you'll do your research, hold your breath, and then hope you made the right decision as you enter your credit card info.
My opinion would be to start with something basic like the O_C then make another purchase a few months later. The O_C can serve quite a few purposes so it won't become redundant in your rack.