If you need to upgrade processing power or throughput, you were already at the end of life of your current computer anyway. Investment in a computer is not easily amortized over traditional payback times, it is a moving performance target that every new application and use hastens the end of its suitability.
Luckily, upgrading can be less than most people assume. What is the constriction points...disk I/O, data in, processing cores, memory? A new populated motherboard is relatively cheap. Terrabyte drives can be added for less than $100. SSD drives for use in processing images are coming down all the time. A small SSD as main disk and a cheap slower large bulk storage drive would get the most bang for the buck with your current hardware. Buying a 6 month old Gamer computer off some neighbor kid would yield breathtaking speed increases, they need REAL power and upgrade often. To them, a 1 year old Gamer computer is worth nothing but will still far exceed the needs of a photographer. Stan St Petersburg Russia