Portable bass options?

I do a lot of music work, and what I am looking for is the best battery-powered speakers with a good bass response (Basically a cheap equivalent to a guitar or bass amp). I also have a netbook that could be used to power USB speakers instead, though in that case the speakers would need to be able to take audio input from a standard audio cable instead of the usb cable. I don't need super high volume either so I'm hoping this is possible.

My AC powered 2.1 Logitech S220 sounds great for my needs, and I've also used my friend's older JBL Onstage which requires AC power, and that has enough bass as well (Looking for a lower range of < 100 Hz), but I'm not convinced to spend the money for the newer battery-powered JBL onstage.

Obviously it should be portable, but it really doesn't need to be super tiny like most ipod speakers, aka smaller boombox sized things are good as well.

(Also please don't bother telling me that I should just find a powered option, etc. I already have those, I'm just looking for a portable alternative to go with the rest of my battery-powered setup)
Thanks for your thoughts and suggestions!

 

I'm PRETTY sure this is what I've used.
Harman Kardon - HK GO+PLAY II - NEWHigh-performance portable loudspeaker dock for your iPod or iPhone.
OR maybe this one which is slightly older. I don't think they made any significant improvements to the sound on the 2nd version.
Harman/Kardon Go + Play Review - Watch CNET's Video Review
Be careful of the much smaller versions tho which are of course nowhere near as good.
The bass is almost too good. Seriously. I have no idea why they only list the power of the tweeters.
I never really used it on battery power. I hope you're not expecting good battery life on anything like this. Although it does use about 8 C batteries.

One thing I noticed that may be convenient for you (and I'm sure no one else has noticed...) it uses the same voltage as most laptop AC adapters.
And, in my case, it used the same plug as some of my laptops. The plug type is Acer/old HP which has a pretty thin barrel. I don't know what netbooks are using these days or if its any different than the rest of the brands models.

I can certainly imagine it being very convenient to be able to use 1 adapter to charge your laptop AND as a backup for your speakers.

 

Oh, and... You said "a cheap equivalent to a guitar or bass amp" ?

I don't know what makes you think that would be possible, it doesn't really make any sense. You are asking for more features, more portability, in fact it would be like saying you're looking for portable laptop that is a desktop replacement but cheaper.

 

I think maybe I'm not explaining too well. I should have emphasized cheap

Basically I'm looking for something like this (which I tried) Amazon.com: Danelectro N10B Honey Tone Mini Amp in Burgundy: Musical Instruments
but with more bass response.

I want to stay under $50 and am looking at speakers like the Wowee one and the X-mini max (though haven't gotten to try them in person), and I'm wondering if perhaps there are options that don't emphasize portability as much and thus can provide better sound quality, especially in the bass department.

 

If you're serious about your music work, buy a pair of headphones. (As an added bonus, they tend to be more portable than a set of speakers. )

JVC HARX700 are within your budget. The Sony MDR-V6 and Shure SRH440 are a bit outside your price range but well worth the money.

 

I have a great pair of headphones, I'm just looking for something that will work when performing in a casual setting for other people.

 

Amazon.com: Edifier MP300 Plus - 2.1-channel PC multimedia speaker system: Electronics
It's not exactly what you asked for, but might give you some ideas.

 

They say... if you want it done right, do it yourself.
Portable Amplifier and Speaker Box Mod by MetkuMods - Because you love your hardware!