Which atmega for a portable console

Hello everybody,
I'm currently designing a "retro" portable console based on the nokia 5110 screen as it's widely available and very cheap. I've already made few promising prototypes, and I'm hesitating about which atmega I should use. I don't need a lot of input/output, I want it to be cheap, and as much flash/ram as possible.

I hesitate between the atmega328 & atmega644. The atmega644 is cool because it has twice the memory of the atmega328, but it's 3x more expensive, far less available, and is not officially supported by arduino, so I'm worried about the libraries compatibility (spi, tone, millis, pwm...).

Maybe 32k of flash is enough (I already made a full game, and it takes 20k), but I think it may be a little short fo really big games... on the other side the atmega644 is expensive and not fully compatible.

What do you think about that ? I think I should go in the cheap and safe way of the atmega328, but... Arh, I don't know. They should do a atmega648.

why not both? it will only be $10. for more capability you might want to consider a raspberry pi.

I dont't speak about building a single, but about designing an open source console for anybody to be able to build one. And I want it to be as cheap as possible. So I was just wondering if the atmega 328 would have enough memory.

I think I'll put an atmega 328 finally because the 644 is far too expensive for a product under 30$ (batteries included), but I'm afraid about the memory.

The 644 is pretty-well supported as far as I can see, however a lot of libraries are written for the 328.

It depends on what you really want. If the game fits into 30Kb, fine. If not, well there's your answer.

For quantity purchases it seems you can get the 328 for around $4 and the 644 for around $7 (AUD). So it's not a lot more money. (And hardly 3 times as expensive). Anyway the ratio isn't that important. If the 328 was one cent and the 644 was 3 times as expensive, that's still only 3 cents.