airport extreme Imac and atv2

hello, ive just purchased the latest airport extreme and atv2 with a Iomega 2tb HD pluged into it to view media, i,m new at wireless as i always used cables to connect things, my question is, my imac connects to my extreme at 300mbits since switching it onto 5ghz, is this fast for wireless and could i tweak somthing to get higher speed, is this faster than a cable or would a cable connect at 1 gig as the ethernet ports are gig ports? also my atv2 connects to the extreme on wireless, how do i find out how fast it is connecting to it and would that benefit from having a cable to it instead, ive read a 100 pages the last few days about how wireless operates but its confusing the life out of me, apart from learning about 5ghz being better than 2.4ghz (well in some peoples opinions)
if somone has as these questions before then i,m sorry in advance

cheers
kev

300Mbps is the theoretical connection speed - i.e. the fastest you'll ever see, full duplex, so the fastest download you could see is half that ~150Mbps (which you also won't probably see) Gigabit is much much faster but you also have to remember your source has to be able to sustain high speed access otherwise you won't see the benefit of gigabit. If I am streaming media I try to wire it. I even use power line adapters to keep my streaming devices wired. The one reason I bought the atv2 is that I cannot run a wire to my bedroom. On 802.11n 5Ghz I can stream fine from both netflix and my itunes library.

5GHz is better in that there is less interference and you can isolate your N network so that no G devices slow it down if you are running simultaneous dual band. The downside to 5GHz is the range is less - so even though you are connecting with a faster protocol range issues may slow you down.