digital conversion shouldn't make anything sound any warmer or colder. You get some dither from up-sampling, and your samples will not benefit from the expanded dynamic range available at 24 bits, since they will be hard locked to their orignial value, or nearest corresponding round-off value at 24 bits. So a sample shoud sound exaclty the same.
You mix of different samples with the effects can however benefit from working at 48K 24 bits. You'll be able to take advantage of the extra headroom, and the increase in sample rate will make your effects crisper.