In my experience the WRT54GL is just as good as a wireless N router in the consumer price range. Despite the claims, wireless N degrades to 72 Mbps over about twenty feet of air. It's not unusual for me to see the signal of my G network one floor away running at 54 Mbps -- the same speed as all three of my N networks at that distance.
So I would say for most consumer applications WRT54GL will be just fine, and if he needs more, either bring the coax right in next to the TV and hardwire the TV to the router with Cat-5e/6, [and/]or buy an 802.11ac router. I've never really seen much difference between G and N, and in fact have found G to be more reliable when the signal forces speed within the G rated range.
You are right that G is better at range, and penetration, than N, but why wouldn’t want a router that supported both? That way you can get great seed when your are in range, but can fall back to G if you want to work out on the patio.
I love the WRT54GL as much as anybody, but it just can’t keep up anymore. Not just the WiFi, but the overall throughput.
It’s puny MIPS can’t push VPN beyond 10 mbit because it has to compute all that crypto with that itty bitty CPU. Even straight up DD-WRT with no crypto pegs my iptables at about 20 mbit sustained. Stock might be a wee bit faster, but you are still pushing an old warhorse beyond anything it was orginally designed to handle.
The TP-LINK puts the crypto onto the Atheros SoC, and with dual G antennas it can push 54+54=108 mbit/s without breaking a sweat.