I like ArmaLite, not the best but darn good. Last year I bought a U15A4C upper for my AR build and it's worked out well. A little muzzle heavy due to the HBAR but not a real problem. Then a few months ago started a new build and bought an ArmaLite stripped lower to marry with that upper.
Yours should work out well, drop in a picture if you can!
If you bought a flat top/A4 one thing to be aware of - if you go with a third party rear sight you'll likely have trouble zeroing because the A2 front sight base only works with "commercial height" rear sights while most are milspec height. What happens is to zero you have to unscrew the sight post so much that it flops around. Flat tops should have an F-marked FSB but ArmaLite, DPMS, Bushmaster and others stayed with the non-flat top A2 height. Since I did buy a milspec rear sight I corrected the problem with a Bushmaster 0.04" taller front sight post (about $5.50). Easy, cheap fix but not widely known.