I am not aware of any "player" that can accept and external input for deinterlacing and scaling, that's the job of a stand alone video processor or high end AV receiver which are out of your budget unless you could get a suitable model second hand at the right price. You are going to have to put up with what the TV's internal processing provides.
The Samsung 51D550 is basically a top end D8000 without the anti reflective screen coating, special screen filter and extra "smart" functionality making it very good value for money.
The Panasonic P50U30A is a basic model with nothing in common with its more expensive brothers the ST30, GT30 and VT30, all of which use a different panel and drive electronics to the U30.
I have not seen the U30 in action but have seen the D8000 in direct comparison to the ST30 and GT30 displaying the same free to air channel and the difference was stark. The ST and GT Panasonic's looked essentially identical and suffered from lots of compression artefacts and noise making the picture look very digital and nasty. The noise filter in the D8000 (which the D550 also has) made a huge difference and did an excellent job of cleaning up the picture to make it acceptable to watch.
I really dont expect the U30 to outperform the ST30 or GT30 so based on my experience I would have to recommend the 51D550 over the 50U30 Panasonic. If you want a Panasonic go for an ST30.
At a 2 metre viewing distance the HD models are not suitable so the field is narrowed to 1080 models only.