Honestly, those A series processors run cool to start with. Unless you plan to try to overclock the A10 past 4.5GHz, you won't need more than the GammaXX 400.
That said, the EVO is a better cooler thanks to larger diameter heat pipes, but it is the same height as the GammaXX 400, so fit would be the same. This means that the EVO can operate at a slightly lower noise level (when using the same fan on both coolers), if that's a factor for you. It's also efficient enough to keep my I7-3930K cool while encoding (with 6 cores / 12 threads) a 48 minute home movie to Blu-Ray when 2 fans are attached.
RE: the side fan... the Spike is a fairly narrow case at just 180mm wide, while these coolers are 159mm tall. About 19mm - 20mm of the difference is taken up by the motherboard, motherboard stand-off's, and height of the CPU on top of the motherboard, leaving about 1mm - 2mm between the top of the cooler & the side of the case.
Would you say that the stock cooler is good enough? I'm only getting a cooler since I read a lot about people having bad temps with their A10 APU's. However, I also read from somewhere that programs can't read APU temps properly hence the high temp reads although I'm not really sure if that's true to begin with or if it's applicable to all APU's.
??? Haven't seen the A10 stock cooler in action, so I cannot say for sure. But I know the stock cooler for my mom's A8 (original Llano series) was horrible, tiny aluminum cooler without heatpipes (looked like it belonged on an original Pentium), temps shot up to over 80C just browsing internet, & computer would lock up after just a few minutes. Put a Scythe Big Shuriken on it & temps now stay under 40C & no lockups.
One reviewer said about the stock A10-6800K cooler (probably same as the 6790K cooler) "AMD stock cooler barely managed to keep things under control at stock"
so perhaps not much of an improvement over the old Llano cooler???