IMO, a room 17' x 17' with a cathedral ceiling is fairly large and challenging. A pair of bookshelves such as a the PSB Image 25's are a good choice (6.5" cone woofer drivers, 91dB, 6 ohms) but you'll need a powerful subwoofer to get you the bass ext and overall balance you'll need. The PSB Image 25's list presently for $479.00/pr. Have you found a pair preowned?