Your setup sounds a lot like mine -- I shoot in my living room (about 12' x 25'), some paper backgrounds, 2 Alien Bees 400s, 1 Alien Bee 800, some umbrellas and some softboxes. I shoot with a Nikon D100 and have found that ALL my lenses work well - my old Nikkor 24-120mm f3.5-5.6; my new Nikkor 70-200mm f2.8 VR and my old 50mm f1.8. There's not one single shoot in the past three years that I haven't found the need to swap out my 70-200 with my 24-120 during a shoot ... and most recently, I've worked my 50mm into the rotation. When I want a shallow DOF, I use the 70-200 and stand WAY back ... sometimes shooting through a doorway, sometimes shooting from half way up the stairs. If I can't stand back far enough, I switch to the 24-120 or 50mm ... or accept a greater DOF and blur out the background in Photohshop.
My two best pieces of advice for you would be as follows -- First, take advantage of the equipment you have and design your shots and creative ideas to work with your current equipment. Second, when you do buy another lens, keep in mind that you won't be in that basement forever ... so buy something that you can use on locations, inside a studio, outside, etc. FYI - I love my Nikkor 70-200mm f2.8 VR because it''s an awesome lens ... and it forced me to get outside more often -- and my new work looks better because of it!
Here's a recent image shot in my small living room -- 70-200mm, paper background, Alien Bees ... and a wee bit of Photoshop to create the lens flares.