I had an xtant 604 amp in my boat. All of a sudden one day someone let the smoke out of it.... Replacements are few and far between and apparently have a lot of gold in them judging by the prices people want. Can anyone make a suggestion for a good replacement? I'm near clueless on stereo parts other than wiring and installing.

Well we would need to know what speakers and how many you need to power.....

2 10" subs, (6) 6" round mb quartz speakers. Not sure models or ratings. I want something very close to what I had because it worked very well

I've been very happy with anything from JL that I have ever owned. I have a JL M600/6 pushing 8 polk 6.5's using 4 of the channels, and the other two channels are bridged for a single 10" sub

You were running all that off of a 4 channel 75 watt amp.

There is what looks like a nice one on Ebay for 250. Why not get that.

Otherwise I would suggest a major rewire of your system. As from what I would guess is they are running 2 channels of the amp on the Polks at 1.5 ohm and then the subs on the other 2 channels brideged at 2ohm. Most modern swtiching digital amps will not like that.

As in the newer class d amps? Ive abused a a/b jbl amp badly 4 spkr's on the front and two subs on the back bridged..it just pounded and pounded 2ohms on the front and 2 on the back

Only one I see on eBay is $350 plus $38 shipping, I would think there are newer more efficient options for $400

The xtant was a great amp......takes me to the days of punch, hifonics, linear power.....

I don't want this to be a rant.......so sorry if I end up on a soapbox.....

Consider the environment....

Motor noise
Wind noise
Water noise
Adjacent boater noise
Female noise....yours and others (skanks included)

What do you really care about sonic reproduction on a high "quality" level?

You want loud......right?

Forget brand....shop price.....alone based on rms, not peak.

Quick caveat....

Manufacturers use a 1k test tone @ 1w 1m ( one true watt of pure digital ac sine measured at 3.3' from the focused dispersion point) to archive the "peak" power rating.

Google 1k. Test tone......not pleasant at all. Same frequency my wife nags in......

Now to class "d".....

Popular definition is "digital"....

No.

Best explanation is "dirty"

Low efficiency but ultra robust MOSFETS do the job (handily) of supplying the output circuits with gobbs of dc current to the subs.

These amps suck for anything above a sub-bass utilization. They are awesome for bass! THD is significantly higher than a tradition A/AB/B/C amp.....but who cares? You can't hear it down there.

"Digital" amps in the 12v realm are few and far between. The limited that exist (real, not claimed...and don't start spewing CEA crap at me, I'm a founding member) are expensive in comparison to like power claims. Efficiency on these amps have astronomical power consumption to power output ability ratios, but do not have a current or future home in an environment we all use......

Please don't get me started on XM and SIRIUS "digital" radio......crok-o-sheet

The system sounded great at the docks, clean loud and crisp. I want quality sound not just real loud sony xplod style lol. But if the cheap high rms rating amps will work I'll look there. I found a good deal on a rockford fosgate r6004d that looks to spec the same as the xtant while reading quickly. I might have to do a few hours worth of reading this weekend.

You forgot to mention the limited freq range of mp3 files..data compression resonant freq using fiberglass...etc...etc...etc.