I have had XPX for a little while now( around 4months) and I used FSX a couple times in that duration and lately I have actually uninstalled my fsx, XPX is whole alot better and you will say the same soon, some planes you may want to look at are the 777, CRJ and the A320neo, they are fabulous. And i basiclly have a FX 8350 and a HD 7870 and i play XPX max out @ 1920x1080, even when taking off and landing at some more of the advanced airports I still have a fluent experience..
I have both the A320 and the Boeing 777. Although, I am loving the A320 alot more than the triple 7 right now, I would say go for the triple 777 first as it seems more completed and just overall better than the A320. But saying that the a320 is geting updates at a steady rate and soon will be ,likely, my favourite plane but saying that the 757 will be out soon.