I'm familiar with how to heat up a boiler. As I mentioned, I did have one boiler at 1k degrees. What was most likely at issue was the length of track I had. The cart simply couldn't keep up and took too long to make deliveries.
Let's say your cart delivers 10 stacks of wood every 10 minutes, if you don't give the 1st boiler what it needs to run for 10 minutes it will run out of fuel and lose heat. The only surplus you can send to the 2nd boiler is what you have left after giving the first boiler what it needs to run for (at least) 10 minutes.
I don't know your setup and I'm sorry if you did that and it isn't working, but I'm suspecting you didn't do that because the first boiler should stay at 1K if you give it all the fuel it needs. And considering you say you think you can run that first boiler if it wasn't for the 2nd boiler I think you're sending wood to the 2nd boiler that the first boiler needs. Just put a chest or a few next to the first boiler (you can't have too many chests, so go crazy if you want) and only send surplus to the 2nd boiler after those are full. Boilers can pull fuel out of adjacent chests/inventories, so use that mechanic to do this.
I'm not trying to argue here, I'm trying to help you find out why your first boiler isn't staying at 1K if it should.
The point is that one SC logger isn't so powerful that it needs a dramatic increase in cost in order to retain its current performance. I just finished setting up a preliminary MFR tree farm setup. Extremely inexpensive for the machines compared to SC, but much more costly in terms of plumbing.
Last time I checked cobble/smoothstone + glass isn't expensive in any amount
Unless you use gold tubing (and don't have a gold farm of some kind) I really don't see how the plumbing has any significant cost, ever.
That said, I really like the cost/reward ratio on the MFR farm and unlike Forestry's farms I can actually wrap my head around the stuff I need to get to make it and automate it. It's not really the cost that's the issue for me, it's the whole 20 layers of crafting that just makes my brain explode and not see what I need to actually get it working the way I want it to.
Edit for giggles:
For those curious about the cost of components for the Galgadorian Wood Cutter that will allow you to operate an SC logging cart at current efficiency (and no durability loss) it works out to roughly:
30 obsidian
21 diamonds
18 magma cream
15 iron ingots
15 fermented spider eyes
15 ghast tears
9 eyes of ender
9 glowstone
That doesn't count the materials for the woodcutting core or stabilized metal.
Ahahaha, yeah I'm not making that. Just like I will never make anything beyond a Basic Drill for a mining cart because I feel anything beyond that is just a waste of resources. The Advanced Drill might be worth the cost by a hair, but the Galgadorian is so expensive it is way cheaper to make 2-3 more mining carts with Basic/Advanced Drills.
And that is only if you're set on mining with mining carts, if you look at other options the SC mining carts just look weak and way too maintenance intensive. And even if they weren't maintenance intensive they still lose speed and efficiency every block they get further away from the "station" where they need to drop off whatever they mine.