Unfortunately, there aren't many low priced catted H pipes on the market. Since X pipes are much more popular than H pipes nowadays, the market is more geared towards those, & there are several affordable catted X pipes available. I personally prefer an H pipe myself.
That being said, MRT is one of the only options, BUT, it is VERY expensive. The quality & fitment of the piece is top notch though. It fits great & is constructed of full stainless steel.
Mustang H-Pipe - MRT Performance Exhaust - 99-04 Mustang
If you are looking for a cheap option, you could pickup & Mac, BBK, or Summit o/r H pipe, & get some high flow cats welded in.
Summit H pipe is $142, & high flow Magnaflow cats are $51 each. Thats $244 for parts & u could probably get a muffler shop to weld in the cats for $50-$100, for a grand total of $344....
Summit Racing SUM-640724 - Summit Racing® H-Pipes - Overview - SummitRacing.com
http://cgi.ebay.com/ebaymotors/ws/e...id=&ua=M*S?&itemid=190217556439#ht_1607wt_941