the theoretical speeds of N far supersede the speeds of internet traffic for most home users. I agree that N should be tried since it is less likely to be congested but if it is not possible out in the garage, I wouldn't worry too much about it since you're not likely to gain that much speed. bittorrents are dependent on a lot of factors like how many seeders there are and the speeds they are seeding at. try downloading an lma mp3 zip of a show in the garage to see what speeds you're obtaining vs in your house, both wireless and wired just to be able to compare.
if you're noticing slow pages loading from either location, I suggest maybe using
OpenDNS. What does this do? Well you register and they provide you two DNS (domain name servers) to use in place of the ones your internet service provider uses. What do you do with these numbers? Login to your router (usually
http://192.168.1.1 in an internet browser) and replace the ISP with theirs. The configuration is really that simple. I did this about 3 months ago (and I believe it was printguy that made the recommendation) and I have noticed 100% decrease in timeouts and pages load much quicker. My computer is connected via cable but prior to the opendns, I would constantly receive page loading errors or very long delays, my two roommates who use wireless also noticed this. They haven't said anything since the change so I'm pretty positive everything resolved (no pun intended).
keep us posted!
btw, opendns is completely free.