Before we get into the pros and cons of the low pressure kit let me say that I have a Tippmann A-5, with the low pressure kit, and a Palmer's Puruit Shop Male Regulator. I did a lot of research to decide whether or not the low pressure kit is worth it and here is what I found out. You can read some of the reviews at pbreview.com - Paintball Reviews and Paintball Fields
. Tippmann claims two things, 1. The Tippmann A-5 STOCK is can use N2/Air. 2. The low pressure kit makes your air system awesome. Now I don't know about awesome, but the low pressure system does replace a number of components in the stock system that could potentially make a difference. I say potential, because 95% of the reviews and tesimonials I have read about paintball are pure placebo. Example: A starfire bolt, I have never seen or heard of anyone (independent, not a company selling the product) actually going through the trouble of setting up a scientific test to determine whether or not it actually increases consistency, reduces ball brakes, and increases accuracy. Either way, the product label tells you it does, and people claim that it works, but I have had a starfire bold on a previous marker and couldn't see any noticible difference. I'm not saying it doesn't work, but rather that no one really has any idea. Some people just want to justify their $25 purchase. Anywho, back to the LPK. One source claimed that N2/Air puts a different type of stress on the parts within the A-5, and claimed eventually the N2/Air system without the LPK would damage and or brake certain stock parts. This may be true, I don't know. Another claim people make is that N2/Air is not as loud. This I think is probably true. The A-5 is loud as hell anyways, far louder than the 98c I used to have. Theoretically, with or without the LPK, if I am used 325psi of air to shoot, and you are using 700-800psi of CO2 to shoot, it makes sense that your marker is going to be louder. However, because of the nature of CO2 and the high pressure, the LPK replaces the main bolt in the reciever with one that weighs roughly 1/3 that of the stock. This being said, less pressure on less mass whould further lessen the sound coming out of your marker. Then again, the A-5 is so ridiculously loud, it's like being 50th in education for a state and then moving up to 45th. Big deal, your kids are still stupid and your marker is still loud as hell. Another point to be made out the new bolt in the LPK is sense it is lighter, it will take less pressure to shoot, thus increasing your air efficiency. All in all, I don't think the LPK is necessary, I bought it because I could afford to and was worried that my parts would break even though that theory is not too founded in reality. If you don't get the LPK and you don't like the results you can purchase it afterwards and install it, it won't mess anything up. As for a regulator I would suggest the Palmer's Pursuit Regulator, I bought mine for $85 new. It's great because it adjusts between 0-800psi thus allowing you to shoot CO2 or Air/N2 whichever you have available at the time as long as you adjust it right. Don't forget to buy a guage as well, should run you $10.