How hot do you want your BBQ to be? A propane grill without lava rocks is fine if you're having small 2-3 hour BBQs and if you're not aiming to become the next Iron Chef. If your goal is to entertain a few friends over the weekend, throwing several patties, chicken wings or steaks on the grill, this is sufficient. Any hotter, your BBQ is going to be cut short and food easily overcooked. Your friends will hate you and never come back.
Oh, and higher BTU does not equate to bigger flames. I'll let aznboi128 edumacate you on this BBQ shizzer.