Well, you could try out
www.fragnet.net they have a FTB starter package which is $17 per month, also 1.5 gb ram, depends if you wish to run plain vanilla or plugins though, I'm guessing just plain vanilla, for that it shouuuld probably be fine, but most FTB packages tend to take up quite a bit of ram, so it really depends what you wish to be doing, if you're gonna go all out and build massive things, you may want to raise the price a bit..
I myself have only tried fragnet, so I know they're good, easy to install the modpack on there, which is done with a few clicks of a button and everything is setup and configured for you, and if you need any help from customer support, with plugins or anything else, they will gladly help and look into it for you. Unlike most other hosts, they actually want to help out, no matter what package you buy. And if you ever wish to upgrade, you can do that in the middle of the month, and the upgrade is done instantly, pretty good, tried it myself. xD
You could also go for creeperhost, never used them myself, but I heard they're good, though customer support is quite terrible, from what I heard.
