You're right. It IS a lot of fun!
The other guys have covered the guns pretty well. I'd like to add two things.
Ruger makes a GREAT cowboy gun. But it isn't historically accurate due to the modern internal action. Some of us want to experience the old style guns more accurately. If you like that idea then you want to be looking at Pietta or Uberti for your guns. The 1873 clones from both of these companies use actions that are either faithful copies or that use a modified spring and plunger for the hand on an otherwise faithful copy of the original "4 click" Colt action.
If you go this route you won't go wrong with either company's guns. I opted to go with Pietta and have zero regrets. The guns started out smooth and are only getting even smoother with use.
If you go for Ruger watch out for issues with the models that have adjustable sights. You can use them in Cowboy Shooting but they are limited to which classes they can shoot in. The safer and more useable Ruger is the New Vaquero.
One thing to watch for is that regardless of caliber the guns come with an overly tall ".45" front sight blade. On .357 guns shooting light loads and light bullets the POI will be low. You'll want to settle on a load that works for you and stick with that load and then file down the front blade until the gun shoots to POA of the sights. For me that means 130gn LRNFP cast pushed by 3.9gns of Tightgroup all put into .38Spl cases. It's a medium speed .38Spl load that is running along at up around 950 to 980fps. It's well above the mouse fart loads used by some but I wanted to feel like I was shooting a gun and not a toy.
My other comment concerns your idea of a Chiappa lever gun. I would suggest you look around for reviews and experiences with this gun and especially the .357 chambered model. Other than the looks of it I have heard only about problems on the inside and precious little good. One of the local smiths cringes when he sees one come in for work because the company simply put too much into making the gun look nice and too little on making it work nice.
If you want to go with an 1892 clone to keep costs down I strongly recommend a Rossi and then get it slicked up. The cost even after the work will still be a lot less. And while the outsides of the Rossi have gone down a few notches for fit and quality of finish the insides of one I slicked up for a friend recently were still good and solid. And in fact the internals of this new gun were even better finished than my own purchased some 4 years ago.
Or buck up and find a nice older "pre-Remlin" Marlin 1894.
Finding a reliable and reasonable costing supply of lead ammo isn't easy these days. And given how much you'll be shooting I'd suggest you reload your own.... which you SHOULD be doing anyway as an IPSC and IDPA shooter. Well... unless you work enough overtime to pay for the cost of factory ammo at least...
Holsters and ammo belts are a whole other topic. You can pay for custom leather or buy off the rack. Myself and a few buddys went with off the rack and bought our rigs from LeatherTown USA through Ebay. Cost was a whopping $140 per rig. But I see that they've gone up to $149 now. All three rigs are doing great going into their third season of regular use about twice a month for matches and practice days. The model we all got was the fully tooled drop leg double holster rig.
After looking around I ended up making my own shotgun ammo belt. So I'm not much help on who has what. But I did find that of the ones I found that they all lacked something.
