A solid turntable setup is a long-term investment that should last you a decade or more if you pick quality components now. Avoid the urge to buy cheap equipment you will just replace in a year, and instead look for gear built to be serviced and upgraded.
Wait for the post-tax return season when manufacturers often drop prices to move inventory before new models arrive. If you find last year's model, grab it; the specs are usually identical to the current ones, but you get a better price.
Remember that the 0% intro APR is a deadline, not free money. If you have a balance left over once the 15 months end, the bank will start charging interest on that remaining amount, which can get expensive fast.