Hi,
It depend on how much professionally wise results you expect?
I think that even with today technologies, we are still not there.
I have tested almost all portable audio recorders.
My target was to find best hand held recorder. Money was not the issue.
I can say one certain thing - all of them have cheap, crappy built in microphones.
Most of them have noisy preamps.
Most of them suffer from poor A to D converters.
My winner is Sony PCM-D1. But even this one is far, far away from to be called professional.
I actually don't understand why in $2000 device, Sony couldn't implement two good sounding mics. Cause mics is the weakest point in this device.
But this fact may partially explain the philosophy behind other brands and their quality. BTW PCM-D1 do NOT have excelent preamps or converters either.
Of course I don't speak about connecting external mics as it makes it less portable and erase the mark "hand held".
Theoretically it is possible to build a small decent recorder.
Put together MicroTrack II as a digital recorder, Apogee Mini Me Preamp and Converter and DPA4021 X 2 cardioid mics and you have a superior hand held device. Well you need to design everything from the scratch to fit in one body. But engineering speaking it's possible.
And the price would be $250 plus $900 plus $3600.
So would you pay approx $4750 for the true hand held pro recorder.

I know it's a bit out of topic and your budget is 10 times less.
But I think that there is a niche for this kind of recorders...especially if someone can half this price down...
Back to your question. Maranz 661 is OK. Sony PCM-D50 is fine. Zoom H4n OK. Tascam DR100 is good. But again, all of them is a compromise between quality and size /price.
If you broad your budget, there are Tascam HD-P2, Fostex FR2 and Sound Devices 702. But then you need to buy two mics... But this is another story.