u/w system support

looking to get a housing sometime this year(currently have 20d) and im just wondering if their are any lenses that a certain system(ikelite, subal...ect) that dont have support for the various lenses out there...

main reason i ask is because im interested in the 10-17 fisheye and i know if i dont have the right port i could end up with heavy vignetting and soft corners... do any of the systems not support a lens like this? or will just a normal 6-8in dome port work on any of the systems?

*EDIT*

and i forgot to ask since the ports glass is in front of whatever lens i use...are the more expensive systems glass better? is putting a lets say ikelite port in front of my lens like putting a cheap filter on?

The Aquatica system does support the Tokina and has dome in both optical acrylic and glass, Peter Mooney a fellow wetpixelian from down under is a keen partisan of this lens (not to mention a bloody good photographer) and is approach is behind a 6" acrylic dome on a Aquatica D2X housing, there is quite a thread, actually one of the longest I ever seen on this forum about this lens, that thread alone and its lenght speak volume about the lens and its quality.