I second most of what has been said above.

Definitely want to add the Pamir Highway to your route. Fergana Valley has some interesting parts but I would definitely chose the Pamirs out of the two.

Turkmenistan is fascinating, both historically and for the rather tragic closed police state it has become. And Iran of course is the cultural keystone for much of Central and Western Asia and it would be criminal to miss it! If you have a Singaporean passport I believe you don't need a visa, but you will still need a carnet, or arrange a TIP (temporary import permit) at the border.

The parts of Kazakhstan which you pass are totally boring and missable. The only interesting bit in that region is Mangystau where you can play in the desert amidst incredible scenery.

The parts of Russia which you pass are very interesting, but if you're planning to just pass through Dagestan and Chechnya then you'll see next to nothing as the highway is on the plain and quite far from the interesting mountains.

So, I would suggest heading south from Uzbekistan either towards Merv (fascinating history - it may once have been the largest city in the world) or at Konye Urgench (itself a nice town, and you can visit the now rather cliched gas crater). Then into Iran, spending as much time there as you can (preferably not in the height of summer). Then you could enter Armenia, which is also an interesting little place and re-join your route in Georgia.

My website (see link in signature) covers all these places.

EO

__________________
EurasiaOverland a memoir of one quarter of a million kilometres by road through all of the Former USSR, Western and Southern Asia.