Having driven a few bog-standard cars recently, I sometimes wonder if I should have left it alone....
That’s exactly what Graham said when out in my car … (I doubt he really entertained the notion for more than a minute though!)
I was particularly impressed with the lack of droning from the exhaust and the ride quality on the original 16" wheels, compared to mine on 17's and with a straight through stainless exhaust.
Having said that, your exhaust was too quiet, you really could hardly hear it at all, so as far as performance upgrades go I'd fit a bigger exhaust from cat back (although still retaining a middle expansion box in some form) and a strut brace and then leave it at that. Any further funds can be directed at cosmetics and suspension refresh when necessary.
My coupe is back in one piece now so you can give it a try to compare the handling on 17's, with a strut brace + new wishbones.
How's your coolant level doing now BTW?