Big fan of the Sidekick, even though I also have a "Full Wimberley" I find I use the Sidekick a little more often. It travels much easier for one thing, and the going from ballhead to gimbal in seconds is a HUGE plus.
The Markins M20 is PERFECT with the sidekick and my go to combo. It's got the smoothest pan! (BH55 is also tops)
On the cheap, the best head option would be the SIRUI K40x, but you'd have to decide if that beefy a ball is what you want for landscapes etc,. but less than half the price of the Markins or BH55.
what lens are you looking at? Your sig show 150-600mm SIGMA contemporary, in which case you could easily get away with "less" ballhead than those listed above. I'm using the Markins with a 500mm f/4 which weighs 8.5 pounds!
Others heads I have tried;
It will do on a SIRUI K30x, which is a little less huge than the k40 and would easily handle that 150-600mm
It works very well on the "Desmond/AKA/SunwayFoto" BH55 knock off which is another bargain head for about $150.00