You most definitely need the crossover to avoid damage to your equipment. Go to the Vandersteen.com website and download the owner's manual for the sub to learn all about it.
It will explain the entire process and what you need to set up the sub. You should be able to buy or borrow the WX-2 temporary adjustable crossover (high pass filter ) that you will need to use. The wx-2 will help you determine the value of the fixed crossover ( x-2 ) that you will then order through a Vandersteen dealer, or else you will wait for one of the correct value to show up here on Audiogon. It may take a while. However, you can use the temporary adjustable filer indefinitely, it just won't sound as good. I suggest that you post a message asking if anyone in your area has a wx-2 that they are willing to lend you. They also show up for sale every so often, for around $20-25.
Note that while the 2W and 2Wq are similar, they are not compatable with each other, so if you plan on getting a pair, you will need to make sure that the second one is the same type as the first.