Spa400

I'm just curious about it.

I have a PSTN line (the phone line very simple). He has no trunk, no caller ID, no other special features. It's just a simple phone line.

My question is, if I buy a Cisco SPA400 SPA9000 and Cisco, will I be able to make local VoIP lines that can be forwarded to my current PSTN service? Can I create my own arteries?

Yes, the SPA400 will bridge between the SPA9000 VoIP lines and your landline local PSTN.
This is assuming you already have a BYOD VoIP provider you can configure the SPA9000 with.

Your PSTN fixed base can potentially accommodate 2 or 3 lines PSTN (FXO) for connection to the SPA400.

Because you have not specified your specific goals other than the bridge between VoIP and PSTN, perhaps the simplest and least expensive to test this to get an SPA3102-NA.
http://www.cisco.com/en/US/products/ps10 ...
The ATA will fill a VoIP line to a PSTN FXO line.
Even two of these projects will cost you a fraction of the investment in the SPA400 + SPA9000.

Assuming you do not have a VoIP provider and does not want to use the SPA9000 as an IP-PBX, then yes, the SPA-9000 will alloy you to connect up to 16 lines local IP extension you can make a route to communicate with your SPA400 PSTN gateway. Of course, these extension lines require IP phones.

The SPA9000 does not hold up to two analogue phones on both FXS lines exist.
Because the SPA9000 handle only two phone lines FXS, I'm not sure I see the advantage of using this system between your PSTN ....... unless you plan to invest in a few IP-Phones that your line extension ...

No VoIP requires a broadband connection to work.

Yes, it works well. VoIP is certainly not need a broadband connection to work the way you describe because it is converted into an analog signal when it leaves your LAN.

Most VoIP services will ensure access to the PSTN using the ATA.