1. VS3251 replaced 251. It does not mean that its improved over 251.
2. Wireless remote does not mean anything to sound Quality. Right? Its just a convinience.
3. I am using the amplified headphone jack on my 251 to connect my HP805 headphones.
4. The RMS rating indicates the power output the speakers are capable of and not in anyway related to sound reproduction quality.
All I said was that 251 is a more balanced set with better sound reproduction. I dont know about 251i, but what I heard is that that variations of 251 introduced into specific markets and some of these are inferior to the original 251 (without any prefixes or suffixes). Get the original 251 if its available or stick with your current set.
Also all multi speaker systems will need some tuning to make them sound to your liking. So you should spend some time on that.