I'm planning on adding 2 Ground Zero GZIW 10SPL subs to my car and I'm not sure what amp to get.
Each sub is about 700W so I was thinking about getting either a 1000W or 1200W amp, I'm open to suggestions and advice since I've just started with car audio.
Ground Zero has the GZIW which appears to be their version of the full bridge mono amps that every other "brand" is selling these days. If you can buy local with a warranty it'll probably be your best option. Vibe brand's powerbox series appears to be the same thing, or should be close enough.
Either should get you by without breaking the bank, but definitely be sure to buy from a trusted retailer who will cover you on warranty should the need arise. I do NOT trust these full bridge amps very far (Brazilian or Chinese made) but odds are if you don't get a dud that fails while under warranty you should get your money's worth out of it.
There may be other brands marketed in the UK that sell the same thing with a different brand name on. Again, I'd suggest the cheap and small footprint full bridge models if you're not looking to really get spendy here. Otherwise GZ probably has a 1200-1500W sized Korean built half bridge which would be of better build quality and reliability but would cost you 2-3X the money.
Finally some might suggest you could run 2000W into those subs but anything much beyond the 1200-1500 tier and you will most likely need additional batteries or upgrade alternator to support it. Stick at that power point as long as you can bear because that's definitely one of the points of diminishing returns along the road from stock to world record holder.
Alternately you may want to price out their 1500w rated woofer. Single 12" will get you pretty close to pair of 10" all things being equal and if you can get a single sub to hold the power you're going to run IMO it is preferable to running multiples provided physical space limits allow.