For all practical purposes an 802.11G router will plenty fast for basic network usage. IIRC 802.11n is a Belkin technology, and isn't approved yet(i could totally wrong here). I haven't really been keeping up with wireless tech as much as other techs, I still run a 802.11b network in my apt, but it's just for my laptop that use for VNC into my htpc.
If you are looking for speed, then just stick to wired, especially if you are going to be large file transfers. Nothing sucks worse then transfering a several gig file across a wireless network and having the signal drop out just before the file finishes.
I don't know about the Linksys SRX, but i'll head off to google in a few minutes.
edit:
http://www.linksys.com/press/press.asp?prid=192&cyear=2005
Basically it's just another variation on the G standard that is proprietary to Linksys. It seems nowadays that every company has their own technology to try and lure people into buying the latest and greatest products, but that is how the computer industry works. If you have the money to go and buy the router and all the cards for all the computers then more power to ya, but I would personally just go buy a WRT54G, and a few PCI/PCMCIA cards for whatever computers I needed and call it a day.
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