A better question may have been, "Where does vinyl end?". As you may have gathered from the enthusiasts here, there's a level of commitment to this as a 'project' that you don't have with a 'plug in and play' digital rig. Nobody has even started on isolation problems, which is another mega thread. You are going to have to get used to the idea of working on your set-up to get it right. A lot of people get turned off vinyl because they don't have the knowledge or patience to make that part of it enjoyable too. If you do, then welcome to the club.
Where to start with vinyl
In your opinion what TT and cartridge would I need to buy to experience a noticable improvement over a Resolution Audio Opus 21 or similar quality ($3-4K new) CD player. Rest of system includes Rogue M-150 amps, Martin Logan Summits and tara air 1 interconnects and speaker cable.