I'm just ahead of you with my first build. got mine moving the other week, a very surreal moment. I'm using a 4s lipo too, despite the norm being 5s. It shifts surprisingly well and the 12v motors don't get hot till after a good 10/15 minutes play time! Regarding esc I'm using hobbywing quicrun duel something. Cheap enough from China via ebay, about £20. Was looking at raglebox and the 85amp one, good esc's but too pricey at the moment with building on a tight budget.
Got any more pictures of your bot to show??