FYI, i having the same issue speedtest on wifi 5-13mbps...

use wifi analyser (android download), check which channel is best for your area.

mine N Only, 20Mh chn 6, i manage to get 28++ for my iphone speedtest, than i test my laptop, still same, suspect laptop wifi card problem, swap the card with newer card, i get 34mbps download and 6mbps upload speed now...

oh ya... if possible just get a L7NR2000 router la, abit old model but for me it not bad la... at least the latency when high transfer rate still maintain 1ms-4ms, innatech RG4332 suck big time, sometime go til 1k of latency.