Coming up in Phoenix, Arizona is an auction offering a choice as red hot as the summers in that part of the world. Weighing in for Germany is a highly modified, effectively bespoke Porsche RUF BTR III packing a staggering 600+ bhp. In the Italian corner is a real thoroughbred: a flat 12 engined Ferrari 512M with a top speed knocking on 200 mph.

On estimates from auctioneers RM Sotheby's, each will set you back the price of a small house - but then these machines are also considerably faster than the average suburban semi-detached home, not to mention considerably less common. Seconds out, then, and let the contest begin.

Porsche RUF BTR III  | Estimate: £260,000 - £335,000  | Year: 1985 | Engine: 3.4 litre flat six, 629 bhp

This remarkable machine may be the fastest example of pure analogue power in a road car. What's more this highly modified RUF BTR III is effectively bespoke, so you won't see another as you break speed records on those autobahn trips to nights out in Berlin. With more than 600 bhp to play with - the result of repeated upgrades including custom cylinder head modifications, a Garrett T04S turbocharger, a six-speed transaxle and engine management by Zytek to Formula One standards - there's going to be very little out there to overtake you. Suspension is unique. Other supercars of the period, such as a Jaguar XJ220 or a Bugatti EB110 SS, are both slower and heavier. This is one serious Porsche.

The RUF BTR III was the ultimate expression of the vision of German obsessives RUF for remanufacturing high end 911s. Here the raw material was already no slouch: a 1985 930 Turbo. The exterior look remains surprisingly subtle, even given the 930's original "whaletail" rear spoiler. The colourway is Porsche's special order Dunkelblau - or dark blue to non-German speakers - now showing the desirable patina of age, while the interior is trimmed in matching dark blue full leather. Specialist wheels are 17-inch Speedlines. It's what's underneath that distinctive rear that counts though: an engine that over several visits to the finest specialists has evolved into a power unit that's as suitable for those trans-continental blasts as it is for a trip down to your local hardware store. Unique.

Ferrari F512M | Estimate: £315,000 - £350,000 | Year: 1995 | Engine: 4.9 litre flat 12, 440 bhp

The visuals are almost subtle, by Ferrari standards of the period. That's not least because exterior paintwork is Maranello's Nero, or black to us civilians, with luxurious beige leather interior and deep pile carpets to match. If the look doesn't scream "supercar", wait until you start up the engine. Open the rear to see this work of art: a mid-mounted flat 12, the last in a production Ferrari, ready to howl its way into your life, not to mention, courtesy an upgraded Tubi competition-style exhaust system, warn others that you're on the way. This is a particularly fast "Modificato" model, denoting numerous engine and suspension upgrades, resulting in a claimed top speed of 195 mph, which most drivers should find just sufficient.

The F512M was the final version of Ferrari's legendary Testarossa models, marked out by the prominent straked cooling intakes ahead of the rear wheels. Just 501 F512Ms were made, marking this car out as super-rare. The Ferrari has led a reassuringly cosseted life under its two previous keepers, with Ferrari specialists dutifully observing the demanding service regimen which can involve taking the entire engine out. Completists will be pleased to note that not only the appropriate tyre foam but also the original tool kit in a leather case by luxury Italian brand Schedoni is present and correct. The gentleman's Ferrari.

Which to choose? We'll leave that agonising decision up to you. Safe to say whoever buys these cars when the gavel goes down in Arizona won't have made an altogether bad choice. And who needs a suburban home anyway?

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