Heck, I only have a 24Mbps download link and everything is crisp including video. My experience is that over about 10Mbps it is the DE servers that affect performance more than the link speed.
Also seems like speedtests are optomised and it is the server RTT that is more important particularly if dropping a lot of packets. This can happen A Lot if you have another router close by on the same channel. Know 1, 6, and 11 are the only clear channels but since my environment is crowded I usually run on 9 since no one else is.