wireless n network and older b/g Express

I would like access and play my iTunes library on my downstairs stereo using an Airport Express with Airtunes. I have broadband internet, an Airport Extreme Base Station with 802.11n, a 2007 MBP Intel duo core running OS X, and an iPod Touch 2G.

Is there any downside to me buying an older (cheaper) used Express with only b/g capabilities? Any interference issues? Internet speed issues? The express will not be near an ethernet access and thus will not be hooked into any ethernet cable. Just to my stereo and the wireless network. I am just wondering if a set-up as described will work well, stream my music library with out delays or glitches, and not hang-up my internet speed on my MBP.

Thanks for any help

I don't think you should have a problem as long as the signal from the Extreme can make it downstairs. The Express was designed for this application.

N routers are fully backwards compatible with B & G technology.

And as regards internet speeds, as I recall, wireless B runs at 11Mbps and wireless G runs at 55Mbps. However, most high speed residential internet connections are only 1 to 6Mbps, so even the slowest of routers is still plenty fast for high speed internet use.