lol, yeah, once you start looking at frames, you can soon talk yourself into a new bike...
I've recently changed my wheelset, as I buckled a rim. I wanted to make use of the bike while the weather was good, so just grabbed a new set, with the thought I could "theraputically" try to rebuild the bad wheel over winter... So, then started looking at a HT frame with the thought I could build up a bike gradually - someone mentioned the Shan on here and the amazing Martini livery, so priced up a build with that and I soon gave up on the idea as a new Whyte 905, Commencal HT AM Essential, or Nukeproof Scout would all be cheaper (yeah, I know they're all ally instead of steel)... I guess that if you already had a groupset, fork and brakes then most of the cost is already done...
As for tyres... I never know, as everything from conditions to tyre pressures have an influence.
I used to get a decent discount with Mavic, so used to run 2.5 Claw Pro front and back, but they're just too soft for the back, so now on 2.4 Quest Pro rear and 2.4 Mountain King 2 Black Chili at the front. I seem to remember the black chili compound making a big difference with the Mountain King, and without it they're pretty meh.