[s-cars] urs4 exhaust system modifications

[Krists]

Hello guys!I'm searching for info about better urs4 exhaust system (sound+performance)+keep in mind that there is no need for extra co2 emission tests in my country!For now I have cut-out the center muffler only..the sound is a little better now but I want a bit louder (not so loud as with no exhaust but the sound with the cats only is awesome,only the fact, that drill around 3k rpm is painful) 
I found a topic in urs4 forum that original downpipe isn't so bad for further upgrades, so I need to know what to do with downpipe-back system?So I came with two ideas: 

1.Replace downpipe-back with 3" pipe +high-flow cat and alternative rear muffler (obx,ractive,remus or smth. else) - so there I need to cut the downpipe before it splits into two pipes! 

2.Much simpler - Replace original cats with needed size high-flow cats, let original pipes stay and replace the rear muffler 
Are there any chances to lost the performance if rear muffler is with one inlet pipe only,like there is necessary to weld two exhaust pipes together again,in case if I can't found an exhaust with two inlet pipes?) 
Please verify some of my thinkings! Thanx!