Bill I'd opt for a TRX 450 muffler, You can still open (HRC Tip) them up when you want or keep them stock quiet when you need. Should still flow more than the 400 can put thru it. Tappers 600 works well with it and they look good.
Ross..
My Rides
1985 250R original (Garage Queen)
-under restoration
1985 250R black and blue full rebuild ( Daily Rider)
-Paul Turner pipe
-+2" Westcoast
1985 Red and White Tecat-EH Sold
1985 Green Tecate Sold
My Wife's Ride
-2003 Suzuki LTZ 400 Showroom fresh and completely stock
My Kids Ride
-2004 Yamaha Blaster, Completely Stock
-2006 Yamaha Blaster, Completely Stock