Schroeder, you hit the nail on the head. There are a lot of choices. It's your money so I can't tell you how to spend it. I'm neither a pro, experienced amateur or even knowledgeable to give advice. I can tell you this much: if you take the advice of the real pros on this site, you can't go wrong.
Before finding this site I sprayed with with siphon feed and pressure pot-fed guns. To save money I bought a set of Devilbiss Finishline guns and gave them a try. They work as well as the siphon guns and a good painter can make them work. I took the advice from the experts on this site and bought an Iwata LPH400 with a 1.4 tip. It didn't make me a better painter but it atomizes the paint so much better than the Finishline that there is no comparison.
I wasn't sure exactly why the Iwata was so much better but one feature stood out. The tulip on the nozzle, where the air and fluid mix, is a plain machined cylinder on the Finishline (tip on the right) and a very intricate wave shape on the Iwata LPH400.
I have no experience with the GTI Pro but if it's a bit cheaper and if that appeals to you, go for it and let us know how you like it.
Your compressor sounds like it can do the job but you don't mention CFM or pressure ratings. In addition, do you have a dryer and filter system able to handle the load and remove the moisture, dirt and oil that can contaminate your paint job? How big are your hoses? A 50-foot 1/4" hose won't flow enough air. What kind of fittings? Are you using big-box store 1/4" Miton M-style couplers and plugs? Those are marginal as well (consider upgrading to V-Style). Two popular sizes, the big T-Style on the left and M-Style on the right, flow 40CFM. The V-Style in the middle flows 74CFM. That higher CFM is what your HVLP gun wants.