uncc_14:
Basically what I need is the speed at the fastest output possible?
.
.
Have you read the previous questions? "The fastest output possible" doesn't convey any useful information. Please quantify "fastest" in some numerical term such as "1k samples per nano-second" or "six samples per fortnight". Then people will be able to recommend a suitable hardware combination.
If you do need a sample rate in the tens of micro-seconds region then Atmel AVR is probably not the right platform and you need to be looking at Cortex M3 or similar.