Help needed--2000 infinity radio

Hi all,

I'm the proud owner of a 1988 Mitsubishi Mighty Max pickup. I come on a mission of peace and discovery from my home forum (http://www.mightyram50.net/vbulletin/forum.php). Long story short, I needed a new radio head unit for my truck and wanted to stick with the Mitsubishi brand. I found an infinity unit from a 2000 Galant (now you know why I'm here) in good condition on ebay and had it shipped. The model is MR490090, same as this listing: https://www.ebay.com/itm/2000-02-Mit...-/142614538257. I picked up a harness that fit and was able to install the radio. It powers on and seems to work just like normal *except* it isn't sending any sound to my speakers. I know I don't have a speaker problem because I just installed new ones and tested them with my previous head unit--they worked fine. So after digging around a lot online I began to think this was an amplifier issue--namely, that this head unit does not have a built-in amp.

My first question: can any one confirm that? And if so, secondly: does any one have recommendations or advice for adding an amp to my model of factory infinity head unit? For example, is there any particular type of amp I should buy? Do I need to go with a factory amp for any reason (something like this or similar, I assume: https://www.ebay.com/p/1423929741?iid=223735098324)? I know the head unit doesn't have RCA outlets, how should I plan to work around that?

For the record, I'm a novice when it comes to car audio, so if I'm way off base don't feel bad putting me in my place. Regardless, I reckon this is not something many people have had to think about--assuming most people using this head unit are also using the factory amp by default and haven't messed with it. But I was hoping against hope that some one here could chime in with some expertise. I would very much appreciate it.

Thanks!
Kevin