I have a TP-Link TL-WDR3600 N600 and it works flawlessly with DD-WRT v3.0-r28015 std (10/23/15).
$59 on Amazon but I got it on sale for $36 from....newegg maybe? I honestly can't remember, it's been a while. I order from a few different sites. Heck, it's $52 at Walmart. Long story short, if you do some shopping around you should be able to get it within your $50 budget, possibly even close to $30.
4 gigabit LAN ports, 300Mbps 2.4ghz wifi + 300Mbps 5ghz wifi (so 600Mbps of wifi to play with if you want to configure your devices to optimize the different bands - ie. dedicate the 5ghz just to media streaming, the 2.4ghz gets shared between everything else).
560Mhz single core Atheros AR9344 v1 rev1.2 processor, 128MB of RAM.
Also had 2 USB ports which I currently have set up with external storage that's shared via samba...
It's a good all around router, look up some reviews. Even with stock firmware it's a good router, and a good deal at around $50 IMO.
EDIT: BTW - if you search for the latest "compatible version" of DDWRT on the router database it shows a MUCH older version (from 2013 I think) but I've had it running the one I mentioned up above for months and it's fine. Not a single hiccup.
Highly recommend this one http://www.amazon.com/gp/aw/d/B008RV51EE/ref=mp_s_a_1_13?qid=1418505764&sr=1-13&pi=AC_SX110_SY165_QL70
I've been using it for 2 weeks and it's been running smoothly without any disconnection with all my Perk devices connected running 24/7. I'd guess the next tier one with 3 antenna would be great too (only $9 more).