I have an Overton Featherweight 48 combo that needs help. The cabinet has at least two blown speakers that I would like to replace. Per Overton's website, the combo is 500 Watts at 4 Ohms. Does that mean that I need to buy speakers rated at 4 ohms? I was looking at some eminence 8 ohm speakers, for example the Delta Pro 8A and 8B. Would there be issues with having two 8 ohm and two 4 ohms speakers in the same cabinet? Speaker suggestions would be great, thanks.