In order to get the particles to integrate well with the fluid at render time you need to enable volume samples override on the fluidShape and increase the volume samples. By default the render engine gets one volume span from the fluid, which is not enough to integrate the density with other volumes when the fluid has detailed opaque bits. Note that rendering can get slow for a high volume samples setting.
In terms of making the explosion more violent you could increase the temperature turbulence. The fast beginning of the explosion may be difficult with simulating the fluid, partly because you need finer timesteps for greater speed, but also because the fluid does not model air compression waves. It sometimes helps to add a second fluid with a purely textural effect (a spherical gradient, with spherical edge dropoff and a little opacity noise)where you animate the fluid scale to simulate an advancing pressure wave. You could also use implode on the noise to make it streak outward from the center a bit like your particle effect. Having that quick pressure poof at the beginning(over just a split second) will help it seem more violent, as well as perhaps having a big short flash(glow). The particles will also help. You can also add camera shake, but I find that tends to be WAY overdone these days.
Duncan
