Koni Yellows and Ground Control coil over sleeves would be your best bet. This will run you between $700 and $800. If you would like to go a bit cheaper, try the Tokico Illumina kit. For around $450 you get lowering springs and adjustable shocks.

As for engine performance, snoopy is right. If you have an automatic, your sure to drastically shorten the life of your transmission.