You are not going to get very far with your 700+ bhp engine if you thing the price of that ebay crank is expensive, an Arrow crank is about £1800 + vat, the rods nearly £850 + vat per set, pistons £650-£750, block £2300-£4500 depending if you supply a block and who/what liners are used and that is only about 30% of what you will spend.
Standard crank and rods are good, but most are nearly twenty years old, would you want to trust them in a 9k rpm big horse power engine ?

Steve

Most of the ebay parts are China's finest either sold via America or Australia or directly imported, good luck.