Ah, I knew I'd forget something... But even so, the first few barrel upgrades are much cheaper than DSUs. A barrel with only one upgrade will hold over 8k, and the overflow could go into your ME system. For many of the sieved items (e.g. amber and quicksilver) I just set up a barrel with a void upgrade just to make sure they didn't flood my ME system when I got over 4k. Same goes for mob drops like arrows and gunpowder. It's nice to keep a bit around, but you'll get way more than you'll probably ever find a use for.