There has been lots written about stainless steel exhausts on this forum.
Your choices are standard, sports or bespoke.
Standard is self explanatory.
Sports is more complicated...Rimmers and Jigsaw sell sports systems.
Rimmers use two inline boxes and are hit and miss regards how well or otherwise they fit (read about it on here....).
Jigsaw use one transverse box and an inline tail box (no feedback since as far as I know nobody on here has fitted this system...?).
Bespoke:
(Probably what you want since you wish to retain the tailpipes?)
I have made up two different systems previously
No.1 Straight (mild steel) pipe from front pipe to over axle section (from Rimmers type system) connected to a T2000 mark ONE (not two) semi sports box
from Chris Witor.
No.2 Inline centre box joined to a Sprint twin tailpipe via a length of flex-pipe. (You need a good silencer c.£100 to make this worthwhile.)
With stainless steel systems you are going to encounter some vibration......
you can reduce this by using mild steel joining sections.
My experience:
Standard stainless steel system....no experience
Rimmer system....I had a Falcon system not bought from Rimmers, it was noisy and had bad resonant vibration 55-65mph

and it didn't last long either.
Jigsaw....no experience.
Bespoke no.1 Much quieter than falcon system but still loud for back seat passengers. No vibration.
No.2 Very quiet compared to others, but slight vibration at 40mph.
So, in summary, bespoke no.2 has proved to be the best for me and also retains the original appearance of the car.
Hope this is helpful,
Ian.