I also started with a Shark pro. Although mine still works fine, I only have a small Bosch trim router on it. We have a Shark HD2 where I work and have a full sized Porter Cable router on it. The work Shark gets rare use as there is so much play in the plastic Z axis assembly that you can't use it for anything more than simple cuts. Some 3D carving where the bit only takes off a small amount of wood with each pass for example. A quick glance at nextwaveautomation's site shows they haven't really improved that aspect of their design.
When I needed more cut room I bought a Probotix Meteor 25 x 50 CNC. It has less usable Z room than the Shark, but is a much more complete configuration including limit switches, an emergency stop right on the CNC frame. It comes with a PC running Linux and LinuxCNC as the control software. IMO a far more versatile control program than the control software that comes with the Sharks. You'll need to come up with software to generate the drawings and G-code with. The Sharks comes with Vectric's vCarve Pro. You can add it to your purchase if you buy a CNC from Probotix.
The bed is MDF which leaves it to you to come up with a strategy for holding parts down. You can get it with a grid of threaded inserts embedded into it. They can be used directly, or you can use those inserts to hold down strips of MDF with t-track in between them. You could also replace the whole bed with t-track. What I value most about the Meteor is that I can reconfigure that bed for whatever I may need to cut with it. Clamping furniture parts vertically or at an angle beneath it is something you can't do so easily with a Shark. I've hung an assembled furniture carcass beneath my Meteor to cut mortises on the bottom for attaching tapered legs that were also produce on the CNC. Probotix also has several options available you can include with your purchase, or add-on later. Touch puck, A tool length sensor (ATLaS), and more. At this time you can likely order one with a heavier duty gantry beam and taller gantry uprights for more Z axis clearance. They are working on an automatic tool changer option as well. I've been able to customize mine for more X and Y travel, faster feed speeds, and much more. You won't be able to change much about how a Shark runs, as their software is proprietary.