David even a used Gitzo Series 5 carbon fiber will run you well over $600. Really Right Stuff series 3 pods are supposedly stable enough to manage a ten pound 600 f4 and there is a used first generation (RRS is now on generation Mark 2) Series 3 at KEH right now for for $782 in Ex+ condition. I have always thought of a Benbo as a tripod for being creative and allowing unusual angles rather than for heavy lifting. If your not going too far from your car a used metal Gitzo series 5 (tele studex) Is reasonable and may be obtainable at a fair price otherwise your talking carbon fiber. The Manfrotto U shaped action head is affordable and substantial. I have never heard any criticism of that head. Some of the larger used Induro and Benro (probably lifted from the name Benbo) pods may work for you and you could find them at auction or sites like KEH for under $500. Make sure you check the specs out before you pull the trigger. Good hunting.