I would not pick a DAC based on tubes or SS, but just on sound. Can a tubed DAC add warmth? Sure. Do they all? No. Take a look at the Audio Aero equipment (I had the Capitole a while back), it has subminiature tubes and imparts a high degree of warmth and bloom while many others do not, the MF Trivista, which also used subminiature tubes (I currently own this DAC, but its just sitting unused) is not what I would call warm or bloomy.
I understand the wanting for the high bit rate chipsets. But let's all be honest with each other, the costs of the chipsets is astronomically cheap (you see 24/192 bit rates in sub $100 equipment). Which goes to show what you are really paying for with a DAC. If the chipsets were the leading component that determined performance, 90% of the HT receivers would be outperforming the best DACs of just a few years ago. But we all know this isn't the case.
Don't get me wrong, I am not saying that the newer chipsets can't improve the performance of a component. But what I am saying is that a DAC with a "great" new chipset, but with a mediocre analog circuitry and power supply will not outperform a DAC with an older, lower sampling rate DAC with a very good analog set-up and power supply.
Take a great older model DAC (great analog and PS) and update the chipset and yes, I think it can improve based on the chip (new technology, capabilities, etc. . . ) but it can only increase up to the capabilities of its weekest links. Just like in a system. You can have a great turntable but a lousy amp and speakers and your system will no show what the table is capable of - same with a DAC with great/new chipset and lousy PS and Analog section.