By "SEP" do you mean single ended pentode? Perhaps if you tell us what amp you're using, someone here will have experience with it and can give you their impressions on how it works with their speakers. Generally, 2 watts will run any model of π speakers and get pretty loud. I wouldn't say they're blaring loud, but they'll surprise you with what they can do with two watts.
As for room size, you have a lot of good choices there too. All but the largest speakers work well in small to medium size rooms. I wouldn't put a seven π-18 in a small room, but I've had seven π cornerhorns with 15 inch woofers in 12'x14' rooms and they sounded very nice. That's a pretty small room for speakers like those, but as long as you sit more than a couple feet away, they sound good.
On the other end of the scale, I like the little one π, two π and two π tower speakers for small rooms. They don't take much space and sound great. If you have a little more room, you might consider the three π or eight π speakers.
By the time you get to the four π, six π and seven π speakers, you're starting to take up a lot of real estate but like I said, they sound pretty good if size isn't a problem and you can sit more than a couple feet away.