Your cpu speeds start to get difficult near 3.6 (air) depending on what type of cooling you are using. 1.4ish-1.45v at 3.6 is common for a8's.
GPU speeds for the k series should be adjustable with a multi in the bios as well. Mid 900's I've seen for the k chips on air. check this with a bench to confirm, it doesn't do squat for the locked chips, and rightly so, but its there and should be easy.
The northbridge in these chips can go 900+, my 3850 nb only liked to go to 930-940 with ~1.16-1.17v. Does help performance to get that up to a nice speed, but is also cause of instability easily.
Mem controller can max out your memory + mobo. Mem speeds are going to be done with your baseclock after 1866 (9.33x) and then everything (cpu/gpu/nb) goes up, but not always reported in bios, so be careful with high baseclocks and high nb multis. High mem speeds will get better gpu performance, but semi-high clocks with tighter timings give the cpu an edge.
Baseclock increases cause vga out issues almost immediately, so use digital outs if high mem clocks are wanted.
AHCI/Raid modes crap out really early on baseclock increases as well, so if you are using an ssd and want ahci mode don't bother investing in great memory, cause it will be untapped.