These mufflers 
http://www.spintechmufflers.com/spin...ctimages/2.jpg are popular in roundy roundy race circles in the US, (the bloke that designed them supplies the majority of Nascar teams with exhaust systems) and they are relatively cheap, (not including freight) and a massive array of configurations in, out, offsets and sizes, as well as very compact in size and as there is no absorbent packing, cant 'wear' out.
From here 
Spin Tech Mufflers
Otherwise, just a good old fashioned glasspack straight through muffler with a resonator near the end of the tailpipe.