M50 exhaust B20, B25 or M20B25 cats

[Kingb]

So I am going to redo my exhaust and can only fine M50B20 cats. Im asking for suggestions:
OBD2 manifolds with
M50B20 dual to single cat, single back to a magnaflow
or
M20B25 cats and pipes to unknown shiny muffler

Just not sure if I wanna put M50B20 exhaust on my B25 but thats all that I can find

[Kingb]

I need suggestions. M20 cats or m50b20 single cat and single back

[Kingb]

Ok so I went with the m50b20 cat and cut off the stock resonator. Fit perfect in the eBay heayders I got. Then I scored a Remus muffler off a 525i for $20 at the junk yard. Which I had to adapt up to the cat. It has a resonated right before the muffler. It is too quite. All I can hear is the task from the the thin headers. I don't get it. I feel like I should have gone with a dynomax to get a little bit if sound.