Don't feel too bad! Remember those National Champ guys roam the country going to National level autocrosses just to get as good as they do. And they've been doing it a lot longer than you have. Those dudes are some serious freaks when it comes to autocross.
I just ran a National ProSolo event this last weekend in Atwater which is 1.5 hrs. from my home. It was fun, but for that much driving, not quite fun enough(let's see, 3 hours of driving every day for three days(9 hours total) for a grand total of 6 minutes of racing just doesn't seem to compute right to me). I didn't have it that bad though, since I went home every night, the guys who came from So. Cal, Oregon, Washington and the like had to stay in hotels. And they do all that just for autocross. They aren't going to waste that much time to come out and get beat by some local who's been doing this, casually, for about 7 months. Oh yeah, there was a National Solo2 at the site the week before which all of the same guys competed in so they had actually been hanging around the area for longer than just that weekend, they'd been there the whole week! These guys plan their vacations and any possible free time they have around autocross. To say they take it seriously and that they will use any and all advantages they can get is a total understatement.
At this event everyone in stock had race tires. There wasn't one guy on anything with a treadwear rating over 50 (basically, either Kumho Ecsta V700's, Victoracer V700's or Hoo$ier'$ autocro$$ tire). Matter of fact, to be competitive locally here you have to run an R compund tire(I just invested in a set of Kumho Ecsta V700's myself along with an extra set of wheels).
In the ProSolo I came in 8th place in front of a guy with a CRX Si from So. Cal. and the guy who didn't show up. I would have been a step or two higher but some misunderstandings about the one of the courses caused me to get a couple DNF's. Also, I have never done an event like this (ProSolo has a drag race style start with a tree and the whole bit and you race head to head against another person on two "identical" mirrored tracks). I was also getting used to the new tires and still getting them scrubbed in so that hurt me as well. I was about 1 second off of the top time in our class on my best run so I feel good about my performance considering all of the factors and the competition level I was in (National Champion drivers).
But I do agree with CJ that at this level the cars are quite different than "stock". When was the last time you went to your local Subaru dealership and got your Impreza 2.5RS with Koni double adjustable shocks? Shoot, single adjustable for that matter? Every car there except mine and one other had adjustable shocks. While the tire rule allows for a pretty insane amount of traction and a tire that you would never buy to run on the street, the shock rule in stock class is absurd! Everytime one of those guys came over and asked about my strut tower bar being stock I asked if their adjustable Koni Yellows were stock. I know I can proudly answer yes when they question my vehicle. The truth is the top guys are really scared of our car. They know as we become better drivers and "development"(read: better tires and shocks, etc.) of our vehicles comes about they are really going to be in some serious trouble.
However, I will never be on their level competition-wise because I don't really want to be. I think autocrossing is a fun thing to do as a way to kill time and some dollars. I went for the gusto this last weekend just to see what it was all about. I think driving any farther than an hour away to autocross is really a waste of time! As it stands right now I have a lot of opportunities to autocross about 15 minutes away from where I live and I'll be fine just having fun right there with fierce competition that exists in my own "backyard". With the occasional trip to the Bay Area(about an hour away) to compete with some friends I've made down there. I enjoy the competition aspect of autocrossing and don't like to do things half way so I'm willing to spend a few bucks on tires, but that's about it. I'm never going to travel cross-country and spend precious vacation time just to autocross.
The unfortunate thing about all of this is that the stock class really isn't about "stock" at all. I see the stock class as an excellent, very cheap way to come out and have some fun in your street car, but the rules allow for so much leeway that guys will spend all kinds of money, sometimes as much as STS or modded classes, to change their cars so they can win.