I order from Cartridge King usually, but I shop around first, comparing CK's price to others. Sometimes Amazon or E Buyer are cheaper, but not often as CK are in Guernsey and thus pay no VAT.
Staples are more expensive than almost anyone here in UK - and I have a Discount Card with them.
My point was that it is very easy to order the wrong cart HERE in the UK, due to several printers using the same engine. So I ensured that I have a record which will give me the right result first time, every time.
I do not use refilled or remanufactured cart's, I only use genuine HP. I have had HP printers for many years and have never had one fail me, using gen cart's. Previous was a big old CP 1700, an A3+ beast that I used in my design & print business, supplying business stationery, entertainment packs, brochures and prospectus books for independent schools. I like HP quality.