I'm getting a Yorkville XS400 combo, and I have a few questions here -- 1. Is it very important to match combo company to cab company? eg, when I buy an extension cab, should it/must it be a Yorkville? 2. How much do Yorkville cabs cost? 3. How's the sound? Durability? 4. Any low-cost reccomendations? Avatar isn't really a great option, because they're mail-order only, shipping it to here (south Ontario), it'd cost a fortune.