Tough call... and it depends on so many factors as to which 'new' pellet grill I'd buy...
If my PG500 were... somehow to disappear , I'd by another PG500 in a heartbeat...
If I came into a big pile of cash, I'd probably do a FEC120...
If I just wanted to explore something new... the Pitts & Spitts pellet grills look nice, I like the 'oval' sort of shape to the Maverick 850 and the 2000...
Yoder still has some appeal to me that's undeniable... The YS640 with the adjustable heat baffle is the one that appeals to me most...
Of course a nice Memphis would also be high on my list of grills to try...
If I were like really ambitious and had money to do so, I'd love to make a custom pit of some sort... One of my biggest complaints about pellet grills is their inability to do cold or at least cool smoking. My PG500 can get down around 160F in cool weather... and I could exploit the warmer drawer with ice and do something cooler... but what I REALLY REALLY want , is a way to generate relatively clean smoke at temperatures bellow 180F on a 80F day... like , one that would burn pellets and actually have a chance of running all day/night long without going much more than 30F above ambient. Ideally it could also go up to 250F on a summer day too... But honestly, If someone made a real pellet smoker that could easily run and put out clean smoke at 30F above ambient, and maybe be able to push up to 100F above ambient and still put out some clean smoke... I'd buy one, if it wasn't like outrageously expensive. What would be really cool... is to have a pit , that had two burners... one for this low temperature smoking... and another for more typical BBQ temperatures... I'd even be happy if the low temp burner was like a add on, using a duct to get the smoke into a larger chamber.