Designs as strange as the above boomboxes are not seen in HIFI, which suggests that they simply do not work as good. Therefore a good boombox should have good acoustically isolated speakers. A good example is in all those portable radios that look like a mini HIFI, like this SANYO, which has a fantastic looking:

The SANYO MCD-850F, a very good-looking boombox with a design closer to a small HIFI.

Although I always preferred a top-level, one-piece designed boombox (a personal taste).

I have seen many "inventions" that claim to offer the same experience that good Hi-Fi boxes, though I imagine the end result was only one wish:

The SANYO MCD-950F, the brand’s top model in 1992. It featured an “bass chamber horn system”.

I heard that model only once in a shop and I remember it was lacking power but the sound quality was not bad at all. However, I find the design excessively ‘organic’ for a music equipment.

Panasonic is a brand that seems to have "hit the mark" with many of its latest boomboxes, as they started from a base design with separate speakers, like the DT75:

The problem is that sometimes they tried strange designs, with  bizarre  speakers like this:

I've never listened how it sounds, but saw no other newer model has them, so I guess they haven’t been “exactly” a remarkable success...

One model that I like so much is the RX-DS30 (probably my favorite from this brand):

I really love it, because it’s compact, simple and elegant design. And it has acoustically isolated resonance speakers. Bravo! The only problem is that it may have not high power (just 11W DIN each channel).

In the other side, the DT680 with its 30W certainly does not have power problems is (I assume refers to DIN Watt):

Panasonic RX-DT680.

Although speakers are independent, I think the side panels being plain have a problem while using plastic as material, because they will be in resonance, which means that the box will not allow to perform their acoustic function perfectly. A simple variation with curved panels are much more rigid, and therefore have better acoustics (I’m supposing that it doesn’t have internal ribs to make them more rigid). Therefore, no good HIFI speakers are manufactured from plastic, but sturdier materials, such as wood.

I recently tested this DT680, courtesy of a good friend, and I can confirm that it sounds great. The bass is powerful indeed, though you have to 'artificially' add XBS (eXtra Bass System) to feel it.

In terms of power, there are extremely powerful some models, such as the A2:

The Panasonic RX-A2, a huge boombox that probably sounds great.
Courtesy of Retro.

But the portable concept is slightly forgotten here... I would rather say it's a kind of portable discoteque, rather than a boombox.

So... is there no boombox that masterfully combines the best from each technology? I mean: a model that has great power, good speakers and the latest technology?

Well I think so, but only found three models. The first two are the Panasonic RX-DT8 & DT9. Here you can see the last one:

The Panasonic RX-DT9, one of the very few 'high-end' boomboxes ever made.

A small beast with pretty impressive features, that includes 2-way acoustically isolated speakers, full-logic full control, dual autoreverse deck, XBS, remote, Dolby B&C, and even manual rec level!

Panasonic RX-DT9, the best boombox made by this brand.
It includes almost every small desirable feature, even from HIFIs.

Although it's impressive, I do not like the design as much as other models. It also looks that the plastic material is one of this matte plastic that easily becomes glossy by using it.

The sound quality is really high, and in pair (and in fact, better) than many mini-HIFIs. The bass is very powerful, specially when you activate the S-XBS system or pull up the lows with the 5-band EQ. However, the bass is still a bit unnnatural and you feel it's mainly created by the S-XBS system. The bass is a bit boomy (bad bass) but has some bits of punchy bass (the good one).