Amazon has refreshed its entire tablet line-up with a replacement for the Kindle Fire HD that adds a few features yet costs significantly less and higher-specified Kindle Fire HDX devices at 7 and 8.9-inches.

The Kindle Fire HDX tablets effectively replace the current Kindle Fire HD devices. They both come with 2.2GHz quad-core Qualcomm Snapdragon 800 processors, 2GB of RAM, Adreno 330 graphics (boasting four times the graphical performance of the existing Kindle Fire HD), and up to 11 hours of mixed-use battery life.

Screen resolutions are 2560 x 1600 for the 8.9-inch version (339ppi) and 1920 x 1200 for the 7-inch (323ppi). The larger of the two is also 34 per cent lighter than last year's model, thanks to Amazon integrating the capacitive touch layer directly on to the glass display. This leaves a lighter single layer instead of the previous two-layer display stack.

Both of the HDX models now feature a front-facing HD camera for video calling, while the 8.9-incher also features an 8-megapixel rear-facing camera, which is capable of HD video recording and comes with electronic image stabilisation and alongside an LED flash. They will both be available with 4G LTE connectivity in the US, on AT&T and Verizon - there is no word yet on whether this feature will come to the UK.

Finally, the HDX tablets come with dual stereo speakers and Dolby Digital Plus audio. They also feature Amazon's new Mayday button. Available 24/7 365 days a year, one tap of the button will engage Amazon's live support.

The refreshed Kindle Fire HD has a slimmer and lighter design than before, but will feature many of the same internals.

Only the 7-inch will be available at launch, with the same quality 1280 x 800 display (216ppi). It will come with a dual-core 1.5GHz processor and dual stereo speakers. Its biggest new selling point is the price, $139 (£87) in the US.

The HDX models will be priced at $229 for the 7-inch and $379 for the 8.9-inch. The 4G versions will be $329 and $479 respectively.

All models will come with Amazon's new Fire OS 3.0 "Mojito" - its heavily skinned Android variant.

All of the tablets are available on Amazon.com for pre-order now. The Amazon Kindle Fire HDX 7-inch will ship from 18 October, the 8.9-inch model from 7 November. The 4G LTE models will ship from 14 November and 10 December respectively.

The new Amazon Kindle Fire HD will ship from 2 October.

UK releases have not yet been announced.