Looking for a bit of wheel advice .

Currently running on standard suspension, 330s wheels 18x8.5 with the 55 offset and 245/40 tyres. I am thinking of xxr's or rotas with 18 x 8.75 or 9.75 , dont mind stretching the tyres a little bit. Might also upgrade suspension in future. So basically ,what can i get away with and will there be any rubbing issues or spacers required. Might even consider the ht autos arches. Cheers in advance !!