You might be surprised to learn that there is not a lot of difference between really expensive and really inexpensive passive controls, when used in some type of outboard box.
You will find that the things that play the biggest role in the sound are the actual value of the control and the interconnect cables themselves.
A high value (100K) can interact somewhat with the input impedance of the amplifier and may cause high frequency roll offs. Conversely, it can also interact with any output coupling capacitor that might be in the source, effectively increasing the cutoff frequency (reducing bass impact).
A lower impedance like 10K will have less high frequency interaction, but will still interact with the coupling cap in the source, and some sources may not be happy driving such a low impedance load.
So you have to be really careful with your setup, and you must keep your cables short, no matter the brand or price. A properly designed and built active line stage can overcome these problems but it is a statement of the poor state of line stages that so few actually bring home the bacon, hence the on-going debate about which is better- active or passive. IME if you do get a good line stage there will be no looking back.
You will find that the things that play the biggest role in the sound are the actual value of the control and the interconnect cables themselves.
A high value (100K) can interact somewhat with the input impedance of the amplifier and may cause high frequency roll offs. Conversely, it can also interact with any output coupling capacitor that might be in the source, effectively increasing the cutoff frequency (reducing bass impact).
A lower impedance like 10K will have less high frequency interaction, but will still interact with the coupling cap in the source, and some sources may not be happy driving such a low impedance load.
So you have to be really careful with your setup, and you must keep your cables short, no matter the brand or price. A properly designed and built active line stage can overcome these problems but it is a statement of the poor state of line stages that so few actually bring home the bacon, hence the on-going debate about which is better- active or passive. IME if you do get a good line stage there will be no looking back.