Believe it or not they actually do some very good ones in ALDI from time to time, mine only cost £30 (wifi, 5-1 mem stick holder, bluetooth, usb) so i just got a converter (£4.50) and installed it myself...
I cant really offer any suggestions on speakers/wiring but you can get some really good quality stuff for £300 I would imagine, even 2nd hand from Halfords do some good stuff.