Well you've got a decision to make, the VSR10 based guns have their weird mag location. But they are the easiest to upgrade and keep running and by far the most aftermarket options. I haven't heard good things about most of the guns with the proper mag location, from what I understand most of them are still passing the BB's up a tube to the normal VSR like location which can cause feed issues.
Myself if I were in your shoes and wanted to upgrade and was buying new I'd buy a JG VSR10 g-spec likely. Then replace virtually everything in there with PDI for the spring, Action Army for hopup and most of the other parts. And I'd Rhop the barrel stock likely polished but maybe tight bore. That will get you going pretty well and cheaper than the TM.
It should be noted I like TM guns allot, my TM VSR10 G-spec has been excellent but it's old. If you had an old one with the non-crimped cylinder and money was an issue I'd recommend going the route I did. Which was using allot of stock parts replacing a few key components and so far it's been running well for 8,000 or so rounds.
Also keep in mind despite having longer range it's still not quite as good as the video's make it out to be;) Yes it's fun, but it's also a patience game, and can be frustrating. After all my work on my gun my biggest problem is wind, because the projectile is so light even running .43g BB's, wind effects the trajectory allot. Reading the wind, and either correcting with windage or tilting the rifle to allow the hopup to counter the wind is the toughest "skill" to learn. Also since the wind is seldom stable at least here, I seldom get a first shot hit. The first shot for me nearly always tells me the wind. Especially between me and the target where there might be a open area etc, so the first shot reads the wind the second shot is correcting and hitting. If you do it fast enough it's not too bad. But I will say lately I've been running my CA M16A2 which shoots almost as hot as my bolt gun or very close, it's very nice to be able to do the same two shot technique but with less delay between the shots and allows me to stay in the scope between the shots.
Luke