Both APC, Rittal, Knürr and HP has rack cooled solutions. By mentioning Liebert I asume you mean Emerson?
A lot of different solutions are available, however some better that others.
My recommendation would be to look at the TCO and ROI when deciding what product fits your needs the best.
Don't forget, that looks can be deceiving The Knürr produkt is ok, but IMHO it has some serious downsides. If you open either the front door or the rear door of the rack, the aircirculation path will be interupted. In basic it means that when the doors are open, you have no cooling. It also takes up quite a bit of space inside the rack.
But like I wrote ealier, look at the combined TCO and ROI of the units you favor. Try to compare different units. They all have good sides and bad sides. Perhaps the Knürr CoolTherm is the right product for your particular needs!
Have you decided with the cooling solution? I think so folks here have given so much information for you. Once my firm was deceived by the looks from a local company offering solutions at cheap prices. So do not give a chance for them.
APC and EMerson (Liebert) mainly have Rack mounted - Depending on your needs there may be other soultion to help the overall room temp. Feel free to email me your requirements and I will see about providing you other solutions.
Thanks for the comment about looks can be decieving. I have to agree as I have bought this way in the past. I think that making sure that it meets your needs and does what you need it to is the best option possible.
Air Conditioned Computer Server Rack
The Knürr produkt is ok, but IMHO it has some serious downsides. If you open either the front door or the rear door of the rack, the aircirculation path will be interupted. In basic it means that when the doors are open, you have no cooling. It also takes up quite a bit of space inside the rack. 
