Metalmeerkat

Something I would add to that is to go for making obsidian tools pretty early on. You need an enrichment chamber to turn regular obsidian to obsidian dust, then a platinum compressor to compress platinum ingots with the dust to make obsidian ingots. Which make awesome tools and armor, equal to or better than diamond equipment. Expensive, but well worth it. Platinum is not too rare, and obsidian is pretty easy to get once you have an existing obsidian pickaxe/paxel.

I assume that other one of the steel ingots you're referring to is Railcraft's steel, which is made from the netherish blast furnace. I say just use the steel created from the respective mod to be used in crafting that mod's items/blocks. My guess is that Mechanism's steel is used more widely.