If you only need a handful of AD converters, then going the dsp24 + ADCIII certainly gives you a quality way to go. It's certainly better than the dsp2000 system (better preamps, better AD converters (Crystal) ...
Hey, rather than getting the DSP24 and the ADCIII, you might as well get the entire SystemIII package. It's not much more money but gives you the entire set of outputs (might wanna use them sometime

). Be aware though, the System III is a dying species. It's going to be replaced by the new (and pretty cool) System3000 (tentative name that is). Will be released around July approximately.
If you were in the US, people should point out the Delta 1010 which also has a better AD conversion than the DSP2000, yet doesn't feature any pre-amps (DSP2000 has 2, the ADCIII has 8).
The Delta 1010 is hugely overpriced in Europe. I've seen for around $1000 ... as oppossed to $520 in the US.
Some people consider the RME Multiface a step up from the D-1010. Great routing flexibility: each input channel can be assigned to every output at the same time with different volumes. Great for different headphone mixes when recording with bands ... flexibility's always a plus). Greatest tech- and driver support. They've got that down at RME. The Multiface doesn't have preamps either. You can get the Multiface in Europe for around $700 (
www.musicians-gear.com or
www.netzmarkt.de/thomann ).
Last not least, if you really want pre-amps with your soundcard, you should check out the Aardvark Q10. Eight channels I/O. Additionally it's got 4 FX sends/returns ... something the I'm sure a number of Delat 1010 users wish they had. Aardvark's been VERY slow at getting drivers out but their products are great once they work properly on your OS. They finally got their final Win XP driver out two days ago (after months of promises). People are happy. Aardvark runs at around $950 in Europe ... $800 in the US.
You might pretty soon want to get separate preamps if you do more than just casual recordings. So, don't make your decision solely on whether an Audio-card has built-in ... don't spend your money on something you're likely to "not" use much in the future ...
In essence, if you have the money for a DSP24 + ADCIII, rather take the real plunge (SystemIII) which is probably a step up from even the Delta 1010 or Aardvark Q10. Comparable to the SystemIII are the RME Multiface (ugly little unit but powerful).
I hate essays ...