re: $1500-2000 M4 build/prebuilt rifle recommendations?

I really like BCM and Daniel Defense. You should be able to find a complete BCM for well under 1500. Daniel Defense seems to have increased in price lately, but you still can find them for under $1500.

For your first AR, you should definitely go .223/5.56. Piston guns are great, especially if you're going the SBR/suppressor route... But there are so many great DI guns out there that I haven't spent the money to go down that road yet.

Something like this would do you well... Just throw on a rear sight and upgrade the stock. You can throw on some rail sections and add other accessories too.

LINK

You would still have plenty of money for a good optic. I prefer Aimpoint to Eotech, but you know what they say about opinions. If you could swing an ACOG, that would be a fantastic choice as well.