It looks like the
Phanteks recently took over the top spot from Archon/NH-D14/Silver Arrow trio as the top air cooler. I haven't seen it being sold in US yet though.
I don't think the size of A50/A70 or even NH-D14 is concerning. It's more of a perception than a real issue of safety for the motherboard. Sure some heatsinks block the 1st dimm, but generally you can raise the fan on a lot of these (esp. NH-D14 and SA). So it's not an issue really unless you have a need to swap ram all the time.
In posts
#19/20 in this thread, I linked some really large air coolers that make NH-D14 look tiny

. Outside of H100, closed loop water cooling still cannot match any of the top 5 air coolers in noise-to-performance ratio, which ironically is the main reason to go with watercooling.
However, there are plenty of awesome ~$35 air coolers without breaking the bank:
- Corsair A70
- Zalman Performa
- Gelid Tranquillo
- Titan Fenrir (i.e., TITAN EC-TTC-NK85TZ/C)
- Thermalright HR-02 Macho
- Scythe Yasya
Directron has most of these.