Yup more then likely if you are looking at inexpensive options PSA will be the answer. Some others would be fine choices as well such as Del-Ton, don't hear of many using them but they always use to get good praise. PSA offers stuff at cheaper prices then almost anybody else and I have gotten quite a few things from them and everything has always been stellar. One thing I will say is if you do decide to go with PSA get their Freedom, or regular/Premium line of stuff as their cheaper Ptac stuff gets so so reveiws with some negative ones thrown in. The freedom line usually is only another $10-20 or so and worth the difference. I am not sure what all kits they still have in stock but there was a few $360 rifle kits just a couple days ago on there and that included everything but the stripped lower which can be had for $40 at a few places. This was the freedom series, most of them are SS barrels which are pretty good shooting barrels.
If you are looking at piecing together a build instead of buying a parts kit then there are a lot more options, you can build a pretty awesome AR for the $500-600 price range with everything being pretty much top tier. The PSA Premium BCG is a great BCG and I have a few of them myself which can be had for $70-90ish depending on sale price. Another great option for a BCG is the AIM V2 Nitrated BCG for $100 shipped (this would be my first pick probably). For lower build kits you can't beat PSA, I just got one of their MOE LPK's with an ALG QPS trigger for $60, the trigger alone is like $40 or more separately so this is a good deal. But typically regular LPK's are around $40-50 depending on what ya want. Buffer tube kits can be had from DeltaTeamTactical for $23. Upper receivers can be had a few places for around $40-50 for stripped upper and add $15-20 more for the Forward assist/Port Door. Usually these cheap uppers are Andersons, which are fine uppers, Schyuler Arms has $60 blem Aero uppers complete right now. And for barrels there are countless great ones out there now days. My first pick would be Faxon Gunner barrels as I am a huge lightweight fan and these are great barrels in the $150ish price range but come without a FSB attached. My next recommendation would be Ballistic Advantage, they also have great barrels just not as many lightweight ones but if you don't mind regular barrels and want one that comes with a FSB already installed then this is the place to go with many barrel options in the $150ish price range. Green Mountain is another great one as well, they make very accurate barrels.
I never hear anyone mention Model1Sales anymore, I don't think they are that popular now days with all the other new companies out there. There are so many places you can order from. My recommendation is to order the PSA Freedom or better yet the Premium line if you don't want to piece your own together. But the ultimate best way is to piece it together with the parts you desire IMO. Hard to beat a $400 complete PSA kit gun for a blaster though.