Most probably it's your source or cable problem. Are you watching Astro with that?

If you are using Astro, then not much you can do since your TV don't have S-Video. S-Video will give a slight improvement. DVD player with HDMI plus upscaler will be more expensive than those without upscaler. Usually those with upscaler will be above RM300. Try to get those. Not sure about Samsung, but the more well known are Sony and Pioneer. I'm using Pioneer DV400 which already been replace by DV410.

The only advantage of buying the same brand as your LCD is you can use the same remote to control both the dvd player and lcd. Other thing should not differ much. Yes, you are right. Unless Astro run on HD broadcast, you will not get much from your LCD. Actually I found that watching Astro on plasma is much better as I just bought a Pana X10 Plasma.