The clash of the tablet titans is intensifying. On Sept. 6, the world's biggest e-retailer, Amazon, unveiled the new Kindle Fire HD in two sizes: Kindle Fire HD 8.9 and Kindle Fire HD 7. It also announced an upgraded version of its current Kindle Fire offering.

The two new Amazon tablets are poised to challenge the best-selling global tablet, Apple's iPad. Amazon's new line-up will also attempt to eat into rivals Google, Microsoft, and Samsung's tablet market shares.

"Their first Kindle Fire tablet was a device that said, 'See, we can tie all this together,' but it wasn't a strong enough device. Now they've really come ready to show that their device line-up is going to be as good as their service line-up. They're tying those two things together, and at a price that is very, very hard to compete with. It's going to push everybody else's price buttons - including Apple's," Forrester Research analyst James McQuivey noted.

Here is a round-up of the two tablets' features and specifications.

Kindle Fire HD: 8.9-inch Version

While competitors like Apple are looking to take the smaller tablet route and are allegedly downsizing with their upcoming models, Amazon has decided to go bigger. The Kindle Fire HD sports an 8.9-inch screen, which is considerably bigger than the original 7-inch Kindle Fire. At 9.7 inches, the current iPad has a larger display, but with the purported 7.85-inch iPad Mini in the pipeline, Amazon's 8.9-inch tablet could be a threat.

The 8.9-inch Fire has a 1,920 x 1,200 ppi resolution, bettering the original Kindle Fire's 1,024 x 600 ppi. A dual-core 1.5GHz OMAP processor is expected to power the device. The HD version of the tablet will be 4G-enabled and offer Bluetooth support. Amazon has also used a dual-band chip for Wi-Fi support, which it claims is 54 percent and 41 percent faster than the Nexus 7 and iPad 3 ones, respectively. The tablet will come pre-loaded with Android 4.0 ICS and sport a front-facing camera.

It will be available in 16/32/63GB versions, which puts the Amazon offering in the same league as the iPad and miles ahead of Google's Nexus 7. Moreover, Amazon will offer dual speakers in this version, a departure from the original Fire's single one.

The Wi-Fi only version and 4G LTE version of the tablet will set users back by $299, and $499, respectively. The tablet is expected to ship on Nov. 20.

Kindle Fire HD: 7-inch Version

With the Kindle Fire HD 7, Amazon has brought about several improvements which were notably absent in its predecessor, putting the device on par with its arch-rival, Google's Nexus 7.

The Kindle Fire HD features a 7-inch screen like its predecessor; however, it sees an increase in screen resolution from 1024 X 600 to 1,280 x 800. The current resolution is the same as the Nexus 7. A 1.2GHz dual-core processor powers the device. Additionally, the HD version sports a front-facing camera and offers Bluetooth support.

This tablet will be available in 16/32 GB version and will be priced at $159 for a non-HD version and $199 for an HD version. According to TechCrunch, the Kindle Fire devices will venture outside the U.S. for the first time and will also be sold in the UK and France. The tablet is expected to start shipping on Sept. 14.