For $500 I'd get
Steel:
http://www.bhphotovideo.com/c/product/504845-REG/Manfrotto_055XPROB_055XPROB_Aluminum_Tripod_Legs.html
Carbon Fiber:
http://www.bhphotovideo.com/c/product/548524-REG/Manfrotto_190CXPRO3_190CXPRO3_3_Section_Carbon_Fiber.html
And a used RRS BH-55 LR:
http://reallyrightstuff.com/rrs/Customkititems.asp?kc=BH%2D55%2DLR&eq=
If you can find one about $300-$350, they come up pretty often at fredMiranda.com which is where I bought mine. If you want to go new, I'd go with this:
http://www.bhphotovideo.com/c/product/554685-REG/Kirk_BH_3_BH_3_Ballhead_with_Quick.html
or
http://www.bhphotovideo.com/c/product/368325-REG/Manfrotto_468MGRC2_468MGRC2_Magnesium_Hydrostatic_Ballhead.html
Steel:
http://www.bhphotovideo.com/c/product/504845-REG/Manfrotto_055XPROB_055XPROB_Aluminum_Tripod_Legs.html
Carbon Fiber:
http://www.bhphotovideo.com/c/product/548524-REG/Manfrotto_190CXPRO3_190CXPRO3_3_Section_Carbon_Fiber.html
And a used RRS BH-55 LR:
http://reallyrightstuff.com/rrs/Customkititems.asp?kc=BH%2D55%2DLR&eq=
If you can find one about $300-$350, they come up pretty often at fredMiranda.com which is where I bought mine. If you want to go new, I'd go with this:
http://www.bhphotovideo.com/c/product/554685-REG/Kirk_BH_3_BH_3_Ballhead_with_Quick.html
or
http://www.bhphotovideo.com/c/product/368325-REG/Manfrotto_468MGRC2_468MGRC2_Magnesium_Hydrostatic_Ballhead.html