I've only had these for a couple weeks, but here goes:
To they sound that good as the review or they are just advertisements?
That's for you to decide, but they sound very good. The reviewers have not over hyped these speakers. They do perform well! You can search the forums for a more detailed opinion.
Someone from here told that they make strange noises sometimes.
They only make a quick noise as they power off after not being used for, I think, 15 minutes. I haven't had any other "strange noises."
I listen too many kinds of music, hiphop/rap/rnb, minimal, electronic, soft and alternative rock, instrumentals. Is there clarity at sound? I don't want too much bass but a good bass, I want balance. Will I be satisfied?
I listen to all kinds of music too and they perform well in all areas. However, I am slightly a basshead and find the bass lacking sometimes for trance & hip hop songs. However, seeing as how you don't need too much bass I'm sure they'll be perfect for you. The bass is very tight and is improved with a proper soundcard/DAC. The key to these speakers is placement. You need to have them elevated to ear height and keep them at least 6 inches away from the wall. If they are too close to the wall you will get boomy bass...
And how is the power?
Plenty of power, for me at least. I've never maxed it out, heh. Too scared.
And now with my preamp/DAC combo unit (the Musiland SVDAC06) it can go even louder.
Any alternative speakers?
Just search on the forums for Audioengine A5. There are alternatives recommended in many other threads.
And which soundcard should I buy?
You might want to look into an external DAC (which can be thought of as a soundcard) to maximize your performance with these speakers. I just received my SVDAC06 DAC today in the mail for $120 on eBay. The difference is quite noticeable and will continue to improve as it burns in more. I'll probably get a mini-review up later. What you can do is search the forums for "budget DAC"s if you want a entry-level DAC. But if you want serious recommendations, you should post a budget.
Do they sound good with IPODS?
Word on the street is that they do since they were somewhat designed for that. Just search on google and head-fi.org and you'll find plenty of information on the Audioengine A5s in addition to what I told you.
Hope that helps, and welcome to the forums!