Ok this is my experience. You do get some vignetting if your lens is wide. 17mm is quite wide and can cause some problems (see below).
I have a 17-50/2.8 Tamron lens with 67mm filter thread.
I also have 2 other older lenses at 72mm filter thread and I have 2x 72mm CPL. One is a Hoya, One is a B+W Kaseman CPL (old version, not slim).
I bought a 67 to 72mm stepup ring and use the 2 CPLs with my Tamron and both causes vignetting at 17-22mm focal lengths. So, I sold both CPLs and got a slim Kenko Pro1D CPL ($90 at OP). Now this one only causes very slight vignetting at 17mm which is acceptable to me.
To go from 67mm to 77mm, you need 2 step up rings. I am not sure if you will get vignetting or not. But it will definitely be thick. Better try in a store like OP and make sure. There is also a single step up ring from 67 to 77mm. I am not sure if it is available in SG. See
here. This might work better. I've not done this since I do not yet own a 77mm thread CPL or lens. You can try.
One more thing, when you start using step up rings, if you intend to leave the step up rings permanently on the lens, You will not be able to use the original Lens hood. If you want to use your lens hood, you will have to take the step up ring on and off with the CPL which is quite troublesome. I leave mine on the CPL permanently but I have a soft filter holder to store the CPL. The normal CPL filter case will not work anymore. You have to consider all the angles here.
As for prices of B+W, you can get an idea from the mass sales thread
here. Definitely not cheap. And I really suggest you get the KSM slim version since your lens is quite wide at 17mm.
So, IMO, for my personal case, I use step up because I have other lenses with larger filter thread. I also sometimes bring those lenses out with my Tamron and I do not want to carry 2 CPLs. I do have other CPLs:
Cokin P 84mm CPL (not threaded)
Hoya 58mm CPL For use with my prosumer Fuji
Tokina 52mm CPL I use this with my 50/1.8, 50/1.2, 55-200VR. Imagine if I have to step up from 52mm to 72mm.. I will look like an idiot.