Yep... I have raced it thousands of hours and you are so right, nothing ever better with 43 real people with the ability to have their own paint schemes seen by all racing on all sanctioned Nascar tracks. It was an amazing time when Sierra/Papyrus ran their servers and crushing when they stopped.
But many hundreds of clubs still race it out there, a good search of the simulator title and leagues usually pop up lists. The hardest part of course is getting the game, especially unopened - you can Ebay it and see prices of $300 or more and it will sell every time. Obviously one of the most collectible sims ever!
Yes, I paid my $29.95 for it and got the most thrill packed ride of my life. Whether against he highly configurable computer drivers or a pack of ranked level 7 racers, I still say the best money I've ever spent.
You can race SERVER TO SERVER with computer cars on the track too - so setting it up with a friend or how ever many you have is ALWAYS a possibility, that is the last and final frontier.
The sad part was that AFTER spending $20 million in perfecting the physics (never to be matched again I believe) Nascar foolishly licenses their sport to EA and dumps Sierra - I think the most foolish move Nascar ever made - and I have seen foolishness from them for years. Every Race is a failure in turnout at the track, they barely fill 50% of the stands and literally block off massive sections. It is partly due to the economy, but it is mostly due to their inability to relate to the fan-base any more.
Will there ever be another racing game like it, no! Will there be a better sim in the Play-Station Genre, obviously graphics today put 2003 season to shame, but that sim was NEVER about graphics, they were just an added feature.