Is the a10 5800k worth the extra 20$ over the A8 5600k?
I will be using it for light gaming, and maybe music production.
It might also be a possibility to get the amd fx 6350 vishera.
I won't be getting a graphics card, so
Will the fx 6350 still be good for light gaming or would the A8 or a10 be better?
I would say the extra $20 is worth it for the A10-5800K simply because it has the "most powerful" integrated grated graphics core. The Radeon HD 7660D is basically slightly faster than a desktop Radeon HD 5570, which means it is slower than the Radeon HD 6570. The iGPU can be crossfired with up to a Radeon HD 7670 for better performance, but it would be less performance than a Radeon HD 7750. Supposedly, AMD's latest drivers allows you to crossfire with a Radeon HD 7750, but I have not seen any benchmarks that would show any improvement; if any, vs just the Radeon HD 7750.
The FX-6300 has a more powerful CPU core, but no graphics card. So you would need to spend more money on the graphics card. Because the CPU core is more powerful than Trinity's, the FX-6300 will give you better performance if you were to use any nVidia card or install something more powerful than a Radeon HD 7750 (assuming the HD 7750 + iGPU does get some performance boost).
The Richland APU, successor to Trinity, is coming out next month. The A10-6800k will have the Radeon HD 8670D iGPU and is supposedly 20% - 40% more powerful than the Radeon HD 7660D. Below is the most up to date info available regarding the performance of the iGPU.
Just to clarify, the A8-5600k, A10-5800k, and the FX-6300 all have the the exact same processor architecture. However, the FX-6300 has 8MiB of L3 cache and an extra Piledriver module (two more cores). With that in mind, single threaded performance (such as Lame mp3 encoding) will be pretty much the same on any of the three, especially considering how they are all unlocked and can easily run at the same speed. Now if you're also going to consider video encoding, then the 6 core FX-6300 is hands down the better processor.
For music production and 1600x900 medium detail gaming, the A8-5600k would be the most cost effective "good enough" solution. It won't play cpu intensive FPS MMOs like planetside 2 very well though (though nothing less than an i5 @ 4.5GHz does, so...).
Also important to note: APUs perform way better in games with 1866 or 2133 RAM than do with 1600, let alone 1333, so don't cheap out on the ram.
I kept hearing/reading that Richland was based on the PileDriver core so I had wrongly assumed that Trinity's CPU core was based on Bulldozer. I guess Richland will be using an enhanced PileDriver core.