I have UMI on my daily driver and they seem to be just fine, but also have a high 10 sec car that improved on 60-ft time after switching to the H-R arms and sway bar with no loss of street manners.
Have the Metco billet LCAs on mine and they seem to work great. Don't really think you can go wrong with any of them (UMI, HR, BMR, Metco, etc.) as they are all an improvement over the stockers.
check out gbodyparts for the spohn suspension parts they look like nice pieces and from what I have heard the are made very well! but I also agree that you can't go wrong with HR's, METCO's, etc I think the only one that I have never like were the a tubular design due to them bending. the boxed type arms seem to all work well. by the way I run the metco's because they are aluminum and I am always looking to shed weight were I can