Who makes the loudest speakers and sound system?

Some of the others like Martin Logan, etc are very good (in fact very very good) but really expensive.

For amplification separate components, amp and pre amp, will get you more power than any receiver. Many times you can bi-amplify these speakers and run multiple amplifiers, ha! more power! Stick with a good name brand amp(s) like adcom and others with a high current capability. When it comes to amplifiers weight really does make a difference. If it says it can deliver 300 watts per channel then it should weigh 20 to 40 lbs. That means no Carver amps, good idea, great engineering, but when put to the test, (high volume dances) they just don't cut it for their rated power, clipping, over heating ect, I've been there. Best and loudest do often conflict. The most efficient speakers that will play the loudest with a given power input often don't sound as good as speakers with a lower efficiency rating. There are exceptions... but most high-efficiency speakers with top-notch sound-quality are very expensive... It would help to know what's really more important to you... quality or quantity?... There's nothing wrong with a system built for "quantity"... lots of fun sometimes!!!

Also... The desired price-range is VERY important. The price range of audio equipment is so vast that I cannot be the least bit helpful in suggesting a system for you without knowing what you want to spend. The BEST stuff costs some SERIOUS money. Did you really mean BEST? Best for how much? Adcom, Parasound, NAD and Rotel make some very high-quality, beefy amps in the $1000.00 range. Bryston cost a little more. AudioSource makes some good budget amps. There are high-end amps costing many thousands of dollars. Pricey tube amps that are believed by many to sound the best. Yamaha and Harman Kardon make the best sounding, most reliable mass-market receivers IMO. Yamaha having an edge on reliability and HK having an edge on sound and current output of the built-in amplifiers. There are receivers by NAD, Rotel, Adcom... Pricier and probably worth it. Could probably get better results without springing for an external amp.