You mention the 72 mhz band in multiple posts posts. In post 4, the specs you give list 35 or 40 mhz. You need to determine exactly what you already have before you think about spending money for something else. The crystals will have a tag that lists the frequency.
All of the radio companies make systems on many different bands because many countries have laws regarding what you're allowed to use.
4.8 volt receiver packs are perfectly fine for most applications. You might have a pack that does not supply enough current (amperage) to run everything.
The packs that come with most radios have 600 mah capacity. I buy receiver packs from "NoBS Batteries" that are 4.8 volt, 1650 mah capacity. There is nothing wrong with NiCad batteries. In some cases they are preferred over NiMH. There is good info about this on the NoBS web site.
http://www.hangtimes.com/nobsbatteries.html