Down-sizing from 18" to 16" on Superb II

Hi,

I'm hoping someone can hold my hnd slightly and give me the vital reassurance I need before I spend any money!

I have a Superb II 170CR 2.0 with 18" alloys (Elegance spec). Driving in Ireland, on crap roads, I'm beginning to get really fed-up of feeling every bump and pothole vibrate through the car. I'm also getting very fed-up of the cost of replacing the tyres every 6 months and the big bills that follow (I drive about 60,000 km per year, so typically get about 6 months out of the front tyres - and I'm not an aggressive driver by any means).

So what I want to do is down-size the alloys to 16". From looking around and reading as much as I can find, I think I'm right in saying that what I need are 16" alloys with a 7.0j ET45 spec. At least, that seems to be the spec if I was to buy new Skoda alloys from an online dealer that they say are suitable for the Superb 170. I was 99.99% sure that I was right, until I had a look at this site. They seem to suggest (unless I'm reading it wrongly) that the 170 2.0 Superb can only go down to a 17" alloy. But the 140 2.0 can use a 16" rim. Does anybody know if that is right or not? I know the 170 is more powerful, but I thought the cars weighed the same, hence my suprise (and confusion). So before I commit to spending some money, can someone please, please allay my fears and tell me it's fine to put 16" alloys on my car? I've read posts on here where people with the 170 are running on 16" rims, so I just want some final assurance really.

Also, on a related topic, does anyone have a thought on running the car on 215/55/16 tyres instead of the normal 205/55/16 tyres? I've read a couple of posts where people are eulogising about the 215's, so just wondered if there were strong reasons for doing / not doing the same?

I'll post this in the Superb owners forum as well (I really need a response as quick as possible as someone is holding some rims for me until I know I can definitely use them), so apologies if anyone gets their knickers in a twist on the double posting.

Many thanks in advance.