My 2004 Dodge 3/4 T was rated to pull 10,500 lbs. With an equalizing hitch, you can easily put 750 lbs+ tongue weight on the Class IV receiver hitch, which I believe will be more than enough to handle the tongue weight of your trailer.
I think your boat dealer should be able to tell you what the total gross weight and tongue weight of your trailer is. You can then check on the pick up truck website of the manufacturer in question (Dodge, Ford, GM, etc.) to check the towing capacity and maximum tongue weight allowed. Tongue weight is usually 10% of the towing capacity.
I think this is a smart choice. To me, trying to pull a trailer that is twice the length and 150% the weight of your X5 is asking for trouble from a safety perspective. Can your X5 tow it? Probably. Would I recommend it? No!
Hope this helps.