We also receive umpteen brochures from the Vantage people every year. We considered them when we decided to do the Baltic cruise next August, but after contacting Vantage and hearing their pitch, we decided to talk with our regular TA (a major cruise specialist) first.
Guess what? We learned that the TA could beat Vantage's price (cruise, air, taxes & fees) by about $300 per person for the same basic accommodations on the same sailing date. Bottom line: I would check Vantage's offer out, but would then shop around before making a final decision. We did and saved $600!