And there is the slippery slope. If you want gear for warm and cold water, that's different from someone who only dives twice a year in Cozumel. As others have said, a 3mm suit isn't much good past 70°-ish, personally I'd even say colder than 75° is borderline for adding a hooded vest or going to a 5mm suit but that depends partly on you and how your body copes with the cold. I have a 7/6mm suit for local diving and a 3/2mm for the Keys, and am thinking of adding a 5/4mm for what passes for winter in Florida. If I dove regularly in Puget Sound or the Great Lakes I'd have already bought a drysuit, but now we are talking serious coin and rentals should be the order of the day before you go that route. See how you can nickle-and-dime yourself into spending big bucks without realizing it?
As far as coldwater regs go, I like Apeks as they are basically bulletproof. The DS4 first stage, maybe the ATX50 second stages or their new XTX100/200 line but stay away from the swivels on the first stage as its far more useless that you would ever imagine. Other good brands I'd consider would be the Zeagles with env seals (the ZX-FlatheadVI or ZX-DSV, not the ZX-50D). Depending on who you ask the piston first stages on the Scubapro regs are either fine for coldwater or will freeflow like crazy, because of that SP has come out with a new diaphram MK17 first stage designed for cold water. My opinion is that a coldwater reg works anywhere, but that isn't necessarily true with warmwater regs. If you like Scubapro then get the MK17 first stage matched with something reasonable for the second stages like the G250HP (you don't need to buy them the way they are bundled in the catalog). PM DA Aquamaster for more advice on SP regs, he works on these all the time and knows them literally inside and out.