The recommended SATA conversion kits are the ones that fit inside the network adaptor, like the ones made by MaxDiyPower or ABitTop
Avoid 3rd party network adaptors, whether IDE or SATA - the one that put most effort in (the GameStar) was based on outdated and inaccurate drivers for the official one and doesn't have Ethernet, everything else is even inferior (and yes, there are knockoffs of both the original and the GameStar)
As an American you can dodge any risk by buying the one with a modem - nobody imitated yet (to date...)
Pretty much any storage solution that (possibly after conversions) is compatible with ATA will work, at least with homebrew; official software using the HDD requires an original Sony disk, but can be modified (ATAD patch) to remove this gratuitous requirement
On top of that, any disk larger than 137 GB will require using software compatible with 48-bit addressing (called LBA48), all major homebrews are and so are some unofficial versions of the HDDOSD (the optional browser update that adds the HDD to the memory card manager)
Also note APA (the PS2 partitioning "table"), combined with the very limited cache you can fit in 2 megabytes of RAM shared with other drivers, breaks down very quickly on pretty much any drive filled more than approzimately 60~120 GB (exact figure is based on number of partition fragments, not size) resulting in significant loading times for just listing all partitions or finding one (ie, there's another reason why the only official disk is 40 GB apart from being a commercial failure)
Finally, to install FHDB and/or HDDOSD the first time, you will probably use someone else's disk image (or hdl_dump's initialize feature) - they work, but the first thing to do should be to run wLaunchELF, go to its HDD Manager, reformat it to get a proper partitioning scheme, and to reinstall HDDOSD/FHDB from an USB drive!
