I will assume you are a fellow Canuck since you are posting in this forum. I would suggest trying
www.fasttoys.net for your aftermarket needs. He is based in Manitoba so you save the cost of brokerage, duty and other fees plus Phil only charges 8% tax. As far as the lids go they are all pretty much the same as far as hp gains go. There is a new one out, though I forget the name of it, that gets a few extra ponies but like I said they have been tested and all fair the same.
Before anyone can suggest to you what a next good mod wuld be, you'll have to give us some idea of your goals with the car and also what you intend to do with it. Are you going to drag it, autox it, road race it??????
The one other thing I can suggest is going with a short throw shifter. Maybe some of the M6 guys can chime in on this one.