98 or upgrade the pro-lite for sniper?

<---dons absetous suit before entering...

Forget range...stick to accuracy and consistancy.  Forget quieting the marker as to do so would require a silencing device and unless you drop the $200 bucks to the Feds for the permit that lets you have one they are illegel (Not to mention not very effective in the paintball world). 

If you have a good, accurate barrel now then you're set. That's the most important part of the equasion.  You mentioned the Stab, that will help in the consistancy department.

Stay with the Red Dot.  The scope is GREAT if you're doing recon work in a scenario game but for use as a Paintball Sighting device, forget it.  One it gives you tunnel vision and two the range of a paintball gun means most tartgets you can hit your can easily see without magnification.

If you are TRUELY hung up on the range part of the equasion, unless you have a Flatline barrel on a marker range for paintball markers will be identical.  I don't know if the Flatline will fit your marker but it does fit the 98C thus allowing it to have greater range.  However, most will tell you that a good, well made barrel will be more accurate than a Flatline and if you are wanting to be as accurate as possible (please try to remove the term "sniper" from any paintball conversations you have.  It only brings you ridicule.) the extra range at the cost of accuracy isn't worth it.

The only marker I know that has long range like a Flatline and MAINTAINS consistancy out to that range is the Warsensor WS-66 series.  However, it is more expensive than either of the options you are looking into and isn't a Tippmann marker (don't know if that makes a difference or not).  The WS-66 is the marker I shoot. (If you look at my sig, it is the marker in the lower right corner).