When you posted this question about Apus Peru, I did a search on this forum. While the company name comes up often, I could not find any reviews of anyone who had actually trekked with them.
We trekked the Inca Trail with Llama Path & were most pleased with their services, as were many others. They also lead a Salkantay trek.
Many other trek agencies offering the Inca Trail trek also do the Salkantay, so you might be better off looking a companies recommended by those who have used their services. I would think that a company who has pleased Inca Trail trekkers would also do a fine job on the Salkantay. Other companies often recommended include Qente & Pachamama Explorers, in addition to LP. From what I can tell from their website, Peru Treks does not do the Salkantay.