All high end GPUs will bottleneck I3-2100, believe me I've ran I3-2100 and GTX 970 in one PC. The bottlenecks did appear when I had CPU intensive games. for your 450W PSU though you can't get 970. your best bet is 960 or you could wait for 1060 when it comes sometime later, but 1060 will most definitely bottleneck your CPU. WHat I did was I got used I7-2600 for 100€ and then got 970 you could go the same way, but get better GPU if you have the money