I am looking for information on Preparative LC's.
My applications consist of large scale separation (5-25g) per run. I am hoping that someone who is using a Prep LC can help me determine which Prep unit will work best for my lab. I have consulted with Gilson, Waters, Varian and HP. Currently I have many Agilent LC's and LC-MS's however thier largest Prep LC only delivers a max of 100ml/min. I understand that Gilson has a unit that will deliver from 5-200ml/min without changing pump heads as well as Waters, however I am curious about how helpful there technical support will be. I would appreciate any information that you could give me.

I would take a look at Biotage, I used them in a previous life and found them to be pretty solid units. The compression modules can end up saving you a lot of money in columns or hassle in packing them.

(No i don't work for Biotage)

If you need larger flow rates, consider Varian's Prepstar. It's a very powerful and good working pumping system.
Theirs RamPack columns are also a good piece of equipment, but I found the NovaSep's DAC columns equaly satisfactory, but less expensive.

(I don't work for neither of them)

I have heard from a reliable source that there is significant pulsation from Gilson single piston pumps at these high flow rates. However, I rate their technical support highly. I can call their 800 number and speak to a tech about hardware or software problems, without even identifying myself. If something breaks, they send you a new or rebuilt part immediately.

I would recomend the Shimadzu LC-8A pump.
It should work up to 150 ml per minute and has such a small pulsation, that it can even be used with MS detector.