Replaced tiny cooler in my GTX 745 (surprisingly, it was not reaching hairdryer-level noise and it had variable speed, but was too loud for me and not very efficient). I stole a bigger heatsink from passive ASUS GF6600, milled and drilled some holes, put some thermal pads and washers, carefully selecting the thickness, so the card doesn't bend with new, heavier cooler. Assembled it with spring-loaded screws and everything is nice and straight. I thought about making some kind of backplate, but probably isn't necessary. It has low rpm 70mm FDB bearing fan, which is quiet at 12V and inaudible at 5V - and the GPU always puts it on the lowest RPM... 69*C in FurMark with fan on lowest setting.
GTX 745 is a rather 'modern' piece of hardware, but I'm using it in a PC meant for XP -> 7 compatibility and lots of legacy connectors for interfacing with old hardware, like capturing DV tapes, or using native floppy drive on modern OS. It's paired with low-power Xeon L5420 on G41MT-D3 board, beefy pico-style PSU and now whole setup runs basically inaudible (that's important for me 😜). Its performance seems to be comparable to GTX285, but at much much lower power consumption.
Earlier I also beefed up the cooling of that pico PSU, because out of factory it was bent like a banana (overtightened screws, no spacers, mismatched thermal pads). I glued some pieces of aluminum to the original heatsink, to make better contact with mosfets, added thinner thermal pads and aluminium profile on the bottom as a support and additional cooling. The model is X1-ATX-180, seems to be pretty capable, 5V line is much better than in smaller PSUs, but the way the original heatsink is attached was a joke.