c-41 is DESIGNED to be run @ 100F, NOT lower. You'll risk cross-over and color shifts(in general) if running at lower/non-designed temps.

I've done C-41 in a SINK(aka water bath) loads of times, and it's EASY to get it tempered and maintain that temperature in a ~1F range(+ 1f is better than -1f, etc.) The larger the sink, the less shifting of temp you'll have. If you can't do it in a sink(preferably an enameled cast iron sink, like a lot of kitchens have), use a bath tub. The larger volume of water will aid you in maintaining temperature more consistently.

I've never used "Blix" kits, and TBH, the chemical binding of bleach + fix has been proven to be less archival. If you just "need" stuff done quickly, like if shooting press/newspaper where speed is key, then a blix kit can work fine since you're not looking for exacting results. If you want OPTIMAL results(it seems many just want it done the "easy" way these days), then I'd go with a separate bleach & fix all day long.

You haven't listed you location on this planet, but if you're here in the USA(shipping costs will be high for int'l), CatLabs is now offering a $100 C-41 kit that has separate bleach & fix.

I'd go with that, and it's designed as a smaller volume kit:


If you're in the UK/EU, then there's a 5L C-41 kit from Fuji(notice it's also cheaper than the 2-bath kit ):