The entire Nivomat upgrade kit included shocks and spring and the heavier bar.

Volvo sells the 22mm bar, but I don't think it would be wise to put it on the sedan unless you get a heavier bar made for the front. perhaps IPD would make a custom front bar for $$$$. No aftermarket performance suspension parts are available to my knowledge. Paul Newman has (had?) a V-8 powered '95 wagon from Converse http://westpundit.blogspot.com/2006/08/volvo-i-should-have-bought-at-13759.html he had the suspension tweaked a bit and I think IPD made the custom bars. I did find a company that makes customer fiberglass springs search engine and it really is up to how much you want to spend.

The sedan came with a heavier rear anti-sway bar than the stock wagon. Jim Bowers has the heavier sedan bar on his wagon and he was adamant that the 22mm would be WAY too much oversteer with the stock springs. I THINK the sean has a 16 mm bar and wagon is 14 mm but it may be something like 16/18. You can hunt for some of Jim's posts as he has the details in his footer.