Hi Andrewzz, welcome to the forum!
SaberForge does offer upgrades from the warrior class to champion class, although I seem to recall reading on a previous post somewhere that not all sabers are eligible for this upgrade for some reason. But I believe most of them are. The cost of upgrading from a 12W warrior (lights only) to a 12W champion (lights and sounds) is $150, plus shipping. Generally, to request such an upgrade, you'd email
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and tell them what upgrade you'd like, and then they'd arrange for you to make payment via PayPal for the upgrade and you'd ship your saber(s) to their address with an RMA form filled out from their website, then they'd finish the upgrade within a week or so and ship it back. In the continental US, the customer pays for shipping to SaberForge, SaberForge covers shipping back to the customer. I'm not entirely sure how upgrades and shipping work for international customers, however.
I'm assuming that since you asked about shipping to Argentina or Chile that you are not living in the US, in which case the shipping on two sabers would be pretty expensive. In the end, if you ordered two warriors now and then wanted to upgrade them later by shipping them back and forth, you'd probably end up spending just as much as just ordering two champions now and only paying for shipping once.
One thing to keep in mind is that SaberForge will be offering lots of Black Friday deals this week. Every day this week they will be posting some great saber deals (up to 30% off) on their Facebook page, and the SaberForge website also runs a lot of sales throughout the year. So you may want to consider saving up for both champion sabers and then waiting for a good sale before buying them
Hope this info helps!