having an all in one box (661, fr2le) makes things very simple. i used to run a stock fr2le and loved it. battery life was spectacular. both the 661 and the fr2le are small, not in comparison with the sony or edirol, but still, very small and i know the stock fr2le sounds great, even for loud music.
i would go with one of those two. i have heard a mod (oade or busman) might be necessary on the 661, but have no experience with the box.
best of luck.