Ahh. A subject dear to my heart!
I do like my toons.
I bought an Amp and a set of speakers to go with it from Maplins.
If you want the actual make & model number, let me know and I'll dig it out.
The amp is bolted to the bulkhead behind the passenger seat.
The speakers are fitted into the top of the boot. You can just see them in this pic.
Probably not the best place with hindsight, but you're struggling for options really. If I were to fit them again I'd have found somwhere under the dash.
Anyway, I blew up my first pair of speakers, so bought some more that were a bit more powerfull. These blew up too, so now I have a pair @ 400w
These are good!
My ipod simply plugs into a socket on the dash, which feeds into the amp. Works well.
Basically though, you're struggling really. Even on my set-up, anything over 50-60mph and your best off with earphones.
You pays your money and you takes your choice. I doubt the ones on eBay for £16 would cut the mustard.
HTH.