You might want to try Bodhi Linux 3.X on a USB stick and see how it goes. That is still based on Ubuntu 14.04 which may work.
You have my sympathies with SiS. I usually encountered this on old desktops so I had a cheap Nvidia card ready to install.
That's the cool thing about a PC versus a notebook, while I like a notebook for room to room or on the go, there's nothing like a PC. Doesn't matter if it's a tower (mid or large) or desktop PC which takes only low profile cards, these are expandable & cards are at all time lows in pricing, and uses less power than ever. Surprisingly, am running the GPU that shipped with my XPS 8700 on this Optiplex 780, though had to install a low profile bracket to use the HDMI port, also has a DVI-D port. Even my HP dc5800 of less specs runs a Radeon 3400 series GPU with twin DVD-D ports (via a DMS-59 adapter, required), that I'd like to upgrade to at least a Radeon 4xxx or 5xxx series for better performance. Or find another of the AMD Radeon 7570 (Dell OEM) that was pulled from it to install in the Optiplex 780.
Here's what the DMS-59 connection coming out of the PC looks like, allows for the install of an adapter (VGA or DVI-D) to drive two monitors, though honestly, it's hard for me to expect a quality experience across twin monitors with a Radeon 3400 series GPU, maybe better with the 4xxx series. Don't know if the Radeon 5xxx series uses these, that's kind of old school stuff, yet lucked up on the DMS-59 DVI-D adapter for $5 shipped, brand new. Though it looks nice on the 20" 1600x900 monitor it's connected to.
One doesn't need an expensive computer to do these things, and I could had easily chosen a tower with a slightly less C2Q (Q9550), and would had, the seller has discrepancies (unintentional) in the listing, at the heading, stated it was a Q9550, on down in the description, stated Q9500, by the time he got up with me to clear the matter up (New Year weekend), it was too late, has purchased the one I got while available. At any rate, the GPU I was going to install in the mid tower wouldn't had fitted anyway, the slot for the GPU was a single one, mine's a dual, and even if it were a single, would had bumped the CPU heatsink.
Poor design on the part of Dell for placing the graphics slot there, most high performance cards requires two slots for install, for clearance. Plus would need either a 6 pin GPU power plug, or would have to purchase a twin SATA to 6 pin GPU adapter plug, just one SATA power plug isn't enough power. Though some cards ships with this adapter, I believe the one in question did. In some cases, this may mean choosing to go w/out an optical drive to have the 2nd SATA power adapter, if used for this purpose, cannot be daisy chained to provide power for other sources. A floppy power connector can also be used, yet will require a Molex to SATA power connector to work, that's better than giving up the optical drive.
Normally, I always find a way to accomplish what I wish to do, as long as there's room to work & power cables to work with, as well as a large enough PSU (350W or higher for the MSI AMD Radeon HD 7770 GHz edition). The spec sheet says 400-450W, many has installed on 305-350W units.
Low cost nVidia cards are plentiful also, just purchase according to need, it's actually my favorite brand.
I was just at the time that I purchased the MSI Radeon 7770, there were no new nVidia cards that featured Displayport, though some arrived on the scene a few months later, and pulled the trigger on the GTX 960, though just a couple of weeks too soon. As EVGA introduced a 4GB OC version of the same card, though with only 128 bit, that's by no means double the performance, though still OC'd out of the box (as the MSI R7770), would had seen & felt some difference under the hood.
These are the kind of things that separates notebook from desktop users, and why it's best to have at least one of each around. Many will give an older, yet still useful, PC away just to get rid of it. I know this from first hand experience, at one time, had so many, had to donate all of the 32 bit ones that I had, the room was piled with these everywhere. Today, I'd recommend a 64 bit PC, even if older, chances are that for less than $20, the CPU can be upgraded for much better performance, and if lucky, may get one that's already been upgraded that an enthusiast has long given up on, moving to newer ground.
With notebooks, you have what you have, other than RAM & SSD upgrades, unless one wants to spend upwards of $800, finding one with a 1GB GDDR5 discrete card is hard to find. On a notebook, since it can't be changed, wouldn't think of purchasing one new with a GDDR3 chip, the onboard may be better.