I have to suggest dillon here as well. I recommend the 650. That will be my next press. Right now I'm running a 550 with case feeder and strong mount. As well as quick change assemblies. I have about 1k in that setup for 9,40,45. When I'm in the rhythm I usually load about 600 rounds an hour. That's with 5 primer tubes already filled and all my prep work done. The biggest reason I'm staying with dillon is there consistency dropping powder. With my autocomp loads ill get it set and I'm done. I check my powder charge every 1k rounds. And in over 15k rounds loaded on that setup I've never been off. There customer service is the best IMHO. I've had to call 3 times for random stuff and they've been great.
Now the reason I wanna move to a 650 is for my pistol loading so I can add a bullet feeder. I trust the powder drop and my eyes enough where I don't need a powder check. Dillon doesn't make a bullet feeder but the hornady one is very easy to install and adapt it to a 650. I load the most for 9mm because I shoot it the most. Training, practice and IDPA.
I was like you op when I was ready to upgrade. I wasn't sure what I would be comfortable at. But I was lucky and got to try rcbs, hornady, and dillon presses all decked out. After using them all I liked dillon the best. The hornady with the bullet feeder was nice but not as consistent as dillon. So I went with the 550 for the manual index and probably 3 months later thought I'm an idiot I should have got the 650. I love the 550 but trust me you will get used to everything and will feel comfortable and you'll be glad you went with the 650. Like others said you can start slow and upgrade later like the case feeder. But once you use one you'll never go back
Oh and as far as your desk, mount it to the wall and buy the strong mount. That mount does wonders for stability.