[Samsung Galaxy Player 4.0, 5.0] obscuresword:
I'm pretty new to this stuff like you as you can see from my join date so I got a lot to learn lol.

http://xdaforums.com/showthread.php?t=1720457 I think I linked this before but let me link it again. This is where you find all the Galaxy Player Rom, Kernels, How to Flash, and etc at. As you can see we have 9 Stock based roms, and 10 non stock based roms. As far as I can tell the stock based roms are usually the most stable. But remember not all of them are in full working order. They have bugs.

For me I only have experience with IcyFusion, Ethereal, and like 3 days worth with R.E.D.D (My current daily driver) lol. I heard/read great things about Klassic Rom and Dream Ultra.

Stability wise it goes R.E.D.D, IF, Ethereal, and then Stock,

Performance wise it goes Ethereal (I think it gives you 384 mb of ram can't remember), IF, R.E.D.D (yes it ups the performance vastly from stock, but I think it manages memory better than the others too), and Stock (is very far behind). However both IF and Ethereal has these weird status bar bugs lol, and some apps on Ethereal aren't fully compatible for some reason.

Battery life also goes to Ethereal believe or not. From Go Power Master app it read I had 84 hrs of battery life (standby), on IF it went to about 60, and on R.E.D.D it's at about 40-45, Stock was like at 30hrs

Soundwise- Now this is weird. I think R.E.D.D sounds the best with Voodoo Mod and DSP Manager, Ethereal has the most bass thanks to beats mod but it breaks FLAC playback :(, IF has the most trebel

I think you should stick with just the custom kernel first and then try out the roms. You may like it better that way. But I recommend R.E.D.D as it is close to stock but offers just more. But I must say that you should try the roms out yourself to see if you like them or not because the best account comes first hand :D

---------- Post added at 03:15 PM ---------- Previous post was at 03:01 PM ----------

Yeah flash a kernel is easy lol. Flashing a rom is pretty much the same, but then you get into trouble with bootloops, black screens, and some other problems.

Well according to hansthesolo (the developer who made Ethereal) he went up to 1.5 ghz lol, and so did a lot of other people without problems. Undervolting/overvolting in my experience cause problems lol. So don't under/overvolt too much because you get weird bugs and shut downs. I like Klins the best. It's pretty much SteveS kernel with more options. Terrasilent, I didn't like it because all of a sudden my player would reboot into CWM and wipe everything, and it was because I was using that kernel.

If those are all your needs, I believe it should. Just remember that even though we have all of these memory optimization for our players, I still wouldn't have like a bunch of heavy memory hogging apps open lol.

You back up from with in ClockWorkMod. CWM replaces the standard recovery when you hold power + volume up. http://www.youtube.com/watch?v=4uo7gHBWNZs if you go to the end of the video, you see backup and restore. All you have to do is have at least like 700mb - 1gb of free space on an SD card.

BTW you did said you have a US Player right?