I have the a CSA VZ58 non restricted. I have the skeleton stock on mine which is what I wanted. There are some decent options for accessories but you don't really need anything. The iron sights are very good. There are side mounts, replacement forends, rear sight replacements to mount an optic but the comb is too low to keep a cheek weld with factory stocks for most people so you either need to replace the stock or raise the cheek piece on the one you have. I would highly recommend this rifle. Mine shoots the milsurp I have(Not sure of it's origin or how to find out. It had Russian looking squigglies on the crates) under 2 moa and after years of service I have still never had a failure with it.
I've heard mixed reviews of the folding kelteks. Aparently 2nd gen are better. I handled them and didn't care for the feel. YMMV.
If pistol caliber carbines are your thing the just right carbine, TNW Aero survival rifle, and thurion defense carbine all have very good reviews from owners. I handled the JR carbine and liked it but I heard stripping and cleaning it can be a pain compaired to the others. They also have take down models. The Beretta is supposed to be very nice and reliable too. I have no experience with it.
I shot a T97 with flat top adaptor for a while and found the controls were not very nice. It also had some failures for me but it was getting quite dirty when they happened. It did shoot really nice when it was working though.
All of those should be close to your budget. Keep in mind if you want to buy extra mags, optics, sling, grips, upgrades, etc. and remember that costs money ontop of your base rifle cost.