I started recently at the same place you're at now. Here's what I learned, and the MUCH more experienced folks here can add their knowledge. You're in the right place for help, as this is a great community.
1. Go ahead and perfect your skills before you upgrade. I have little doubt that you'll discover new wants and needs along the way and you can make more informed decisions.
2. A single infrared lamp doesn't get the part up to curing temperature without lots of help from reflectors, etc. Even after experimenting with "improvements" I was never able to get infrared to work for me. It seems ovens are the way to go. I'd hate for you to get one thinking, like me, that it would cure powder without help.
3. When you're looking at costs, remember to factor in the oven AND the wiring cost. I had a good gun (Caswell 50v system) but found out the hard way that I needed an oven. $25 and a short trip to a condo that was being remodeled scored an oven. Lots of elbow grease later, I had a clean oven that still smells vaguely of bacon... I'm expecting dogs to salivate over my car when it's done.
4. Now I have to wire my garage for 220v. I have 220 at my compressor, but it's on a 20-amp breaker and I need a 50-60 amp breaker to support the oven. Not a huge deal, but I planned on being finished with the powder on my front suspension at this point, and I'm working on these side issues with the front axle and shock towers half-cured and sitting on the workbench waiting for the oven.
This isn't such a problem for me as I'm not on a timetable and the extra money isn't really a big deal after I Ebay the infrared light.

However, I'd much rather plan ahead. If I had the need, I'd build a really nice oven, but I'm limited on space at this time, so I'm going to "pregnate" my used oven.