Class A power amp will give the best BASS SLAM?

Plinius. Various models available!

The preamp plays a vital part in bass slam as well. A good preamp can give you added slam if the amplifier is up to the challenge.

A major consideration in answering your question regards the partnering speaker, as well as the rest of the components, which you didn't indicate. An amp alone doesn't slam, it's the complete system that all contributes to the end result in this area. One can have a very high quality amp that will deliver tons of current with a high slew rate and still have a compressed result if the speakers are not capable of delivering dynamically. So system context and room size all play critical roles in the final outcome. There is no simple answer based on the amp alone. What do you have in mind?

Best bass slam like everything else in audio is a relative term.

However, the tighest, deepest, most well-defined, and most natural bass I've yet heard come from the Nuforce Ref. 9 amps retailing new for $2500 a pair.

Of course, The Absolute Sound directly or indirectly comparing these little analog switching amps to the $35k ASR Emitter II amp (their favorite) and a few others in this category may help substantiate my claim. Not to mention TAS giving these Nuforce amps a Golden Ear Award and Amplifier of the Year Award.

Second runner up was my McCormack DNA-2 Revision A class A/B amplifier pushing 600 wpc into 4 ohm loads but that amp is over your budget.

What you are after is an amplifier that takes absolute control over your woofer's drivers.

And though proper amplification means everything in this regard to absolute bass slam, control, etc., speakers, speaker cables, ics, dedicated circuits/lines, speaker placement, line conditioners, racking systems, and just about every other aspect all play significant roles toward achieving this goal.

In other words no component is an island. One serious deficiency in any of the above categories and you may never know what your amp is truly capable of delivering.

After about 90 hours of burn-in and seeing what the Nuforce amps did in comparison to my now dearly departed yet still beloved DNA-2 Rev. A amp, I immediately sold that amp and became a dealer for Nuforce. So my opinion here should be considered a biased one.

And for what it's worth, my speaker load is 4ohm at 86 db sensitivity and recommended power rating is up to 500 wpc. That's a pretty demanding load by most any standard.

-IMO

and the speakers are?