I'm not sure how much help this will be but I drove my Vandersteen 3A Sigs (87 dBL) in a room about your size with my Aleph 3 and found it did not have enough power for me. The 30.8 may be different but the Aleph 3 is also a 30W amp and the speakers are close in sensitivity.
When I used this combo in a smaller room it worked well. Once I moved to the larger room it didn't.
When I used this combo in a smaller room it worked well. Once I moved to the larger room it didn't.