It was Manetho who recorded Khufu as Suphis and there is no Egyptian "Horus name" (inside a serekh) for a pharaoh named Suphis.
Khnum is a deity. It was adopted like 'Aten' and incorporated into Akhenaten or like 'Amun' was incorporated into Tutankhamun. It is a common practice and the evidence inside cartouches attests to this. The name of the deity appears first due to honorific transposition - the idea that a deity is more important even than the pharaoh - but it is usually pronounced at the end of the name: as in the two examples I have just given.
The other two names for a pharaoh which are almost exclusively always written inside cartouches - the praenomen ('nsw bity' name) and the nomen (birth name) - do not exist anywhere in the archaeological record to give substance to the name Suphis.
Khnum-Khufu and Khufu, however, do exist in various forms in various places, lending arguable weight to the name Khufu. Like, below, taken from Wadi-Maghareh. The name Khnum-Khufu can be read in the cartouche.
New evidence regarding political activities under Khufu's reign has recently been found at the site of the ancient port of Wadi al-Jarf on the Red Sea coast east of Egypt.
In 1954, French scholars François Bissey and René Chabot-Morisseau excavated the harbour, but their works were stopped as a result of the Suez Crisis.
In June 2011, an archaeological team led by French egyptologist Pierre Tallét and Gregory Marouard, organized by the French Institute of Oriental Archeology (''IFAO'') restarted work at the same place.
Among other material, a collection of hundreds of papyrus fragments were found at the site. Ten of these papyri are very well preserved. The majority of these documents date to the 27th year of Khufu's reign and describe how the central administration sent food and supplies to the sailors and wharf workers. The dating of these important documents is secured by phrases typical for the Old Kingdom period, alongside the fact that the letters are addressed to the king himself and Khufu is addressed by his Horus (serekh) name. This was a typical behaviour when an addressed king was still alive; when the ruler was already dead, he was typically addressed by his praenomen ('nsw bity' cartouche name) or his nomen (birth name). This makes sense, especially so given that the AEs regarded the pharaoh as the 'living Horus'.
Post Edited (10-Jun-14 19:06)