The Speedtouch 510v6 is actually the cheaper Broadcom chipset, 6338. So is the 585v7. The 585v6 was a 6438. The 585v8 is Infineon, so not Broadcom at all.
We do have DG834 v4's in stock which is your best bet as it's a 6348 (no real difference to 6358 IMHO)
Is the correct answer the other specs for the chipset of the 585v7 incase anyone was still interested are
Flash: S29GL032N90TFI04 (Spansion 32 Megabit)
RAM: DS1216AGTA-75-E (Elpida 128 Megabit)
Dunno who said it was a 6348 chipset but obviously they dunno what they were on about.
The 6358 chipset (depending on model of router it is in) is capable of running at a higher clock speed than the 6348 and makes the 6338 chipsets look very poor in comparison. (the 6348 and 6358 are faster). The 6358 is not only capable of wireless N and faster clock speed over both the 6348 and 6338 but also can be teamed with higher amounts of Flash and RAM. (Again though that will depend on actual router model).
For the most part a BCM6348 chipset will suit most people fine (unless they insist on using what i deem is the pointlessness of wifi on any router even N rated). Its a resonable paced chipset has a decent amount of RAM in most cases and is reliable.
The Thomson 585v7 which so many providers seem to give away like smarties with its horrid 6338 chipset is a nasty slow heap by todays standards.