What power conditioners can convert 230v to 120v?

Try to avoid "converters". They are usually cheaply built autoformer-based. rather than a true transformer. If you do require a step-down transformer, check out used items on Ebay. I just picked up a regulated one for $29 that would have been over $1200 new and their lifespan is often decades. You would need to know the maximum amp draw of the components and multiply by 2 (roughly).

I've read two similar but different things about using 60Hz transformers on 50Hz. One wrote that the transformer should be derated by 17% to 20% (50/60). The other wrote the input voltage must be 17% lower than the maximum rating.

The latter being from: http://www.solaheviduty.com/support/faq.html

The Sola portable (120V) I do have is quite noisey, but probably not indicative of the type or brand. With hard wired ones, there have been effective installation options.

Sola is one of the few I've seen offering 50Hz models (group IV) in both general purpose and regulated.